The 24-year-old South Korean player made a 20-foot birdie putt on the par-4 first, while playing partner Lizette Salas had a double bogey for a three-stroke swing.
''That made my day much easier, that's for sure,'' Park said. ''I holed a long one on the first hole. A birdie start is always a good thing. That gave me a lot of confidence.''
''It had been a while since I won a major,'' Park said. ''It feels very special. This week, I played very solid. Today and all week, I played very good.''
Park celebrated the victory with the traditional leap into Poppie's Pond, and jumped from fourth to second in the world with her fifth LPGA title and ninth worldwide win. South Korean players have won three straight majors and Asians have won eight in a row.
Park was four victories in her last 16 events. She won the LPGA Thailand in February in her season debut when Ariya Jutanugarn closed with a triple bogey to blow a two-stroke lead.
''I've played five tournaments on the LPGA tour and I've won two of them, which is a very good start,'' Park said. ''It's pressure off me for the rest of the season.''
Last year, Park won twice, had six runner-up finishes and topped the money list. She won the Evian Masters in July in France, tied for third in her next start, added three straight second-place finishes and capped the six-event run with a victory in October in the LPGA Malaysia.
''I've seen Inbee do this before,'' top-ranked Stacy Lewis said. ''I played with her at Evian last year when she had I think 22 or 23 putts in the final round. When she rolls it, you can't beat her. She's the best putter on tour. The course here is a little softer than normal, so I think that's to her advantage.''
The 22-year-old Ryu, playing five groups ahead of Park, shot a bogey-free 65 - the best round of the week. Ryu is close friends with Park and they played a practice round together before the tournament.
''She looks like she played another golf course,'' said Ryu, the 2011 U.S. Women's Open champion. ''This golf course is really hard, and especially before we start the tournament, she really worried about the game because her ball flight is a little low, but this golf course has pretty firm greens, so she said, 'Oh, I don't think I can stop it on the greens because my ball flight is too low.' ... I think she was lying to me.''
Salas, the 23-year-old former University of Southern California player who grew up west of Los Angeles in Azusa, had a 79 to tie for 25th at 2 under.
''Obviously, I'm not very pleased,'' Salas said. ''Very disappointed in myself. ... Starting off with a double wasn't in the game plan, but everyone is going to have those days where they're just not going to be able to score.''
Any drama evaporated on the first hole on another hot afternoon in the Coachella Valley.
After Park smashed her drive down the middle, Salas - dressed in Trojans cardinal and gold - hit into the deep left rough, 30 yards behind Park. Salas topped her second shot, advancing the ball only 15 yards.
''The second shot, it just came a little too quick,'' Salas said. ''Throughout the day, I was just really anxious and hit a lot of pulls today. I was just not myself today.''
Still in the thick rough, she left her third about 15 yards short of the green. Salas chipped to 15 feet, watched Park hole her birdie putt, then missed her bogey attempt and tapped in for double bogey.
Park increased her lead to seven on the par-5 second, holing a 7-footer. She stumbled on the par-4 sixth after driving into the left-side water, ending her bogey-free run at 27 holes.
Showing off her considerable putting prowess, Park made a 22-footer for birdie on the par-3 eighth and got to 15 under with a 5-foot putt on the par-5 ninth. She dropped another stroke on the par-10th, leaving her with a four-stroke lead over Ryu.
Park made a 25-foot birdie putt on the par-4 12th and a 10-footer on the par-4 13th to push her lead back to six at 16 under. She nearly made it three straight birdies, but her 12-footer lipped out on the par-3 14th. She missed a short putt to bogey the par-3 17th, and closed with a par.
Lewis, the 2011 winner, tied for 32nd at 1 under after a 72.
After winning consecutive events in Singapore and Phoenix to take the top spot in the world from Yani Tseng, Lewis tied for ninth two weeks in Carlsbad and was never in contention at Mission Hills.
''It's been crazy,'' Lewis. ''I expected to get the attention at the tournaments and at the course, but I've been surprised at things off the course.''
DIVOTS: Park earned $300,000. She's the third South Korean winner at Mission Hills, followingGrace Park (2004) and Sun Young Yoo (2012). ... Tseng closed with a 74 to tie for 48th at 2 over. Winless in more than a year, she dropped to No. 3 in the world. ... Lydia Ko, the 15-year-old New Zealand amateur who won the Canadian Women's Open last August to become the youngest LPGA Tour champion, had a 69 to tie for 25th at 2 under. ... Natalie Gulbis also shot a 69 to tie for 32nd at 1 under in her return from malaria.