Harman, who is attempting to join Tiger Woods as the only golfers to capture back-to-back Junior Amateur titles, defeated Glenn Northcutt, 5-and-4. The 17-year old Harman won two of the first three holes and three of the final four to close out the match.
Woods won the event three straight years from 1991 to 1993.
Harman, a native of Savannah, Ga., will meet Kyle Stanley in Thursday's round of 16. Stanley, 16, bested Marc Gladson, 2 up, in his first-round bout.
'A lot of people are looking to beat me,' Harman said. 'But somebody else has to play good to beat me. I'm striking the ball really well.'
Other winners on Wednesday include Matt Savage, the second-seed in the field; 2003 U.S. Open qualifier Tom Glissmeyer; native Koreans Sung Kang and Steve An and 14-year old David Chung, the youngest player remaining in the competition.
Harman fired a 7-under-par total of 133 during the two-day qualifying portion of the tournament, eight strokes better than second-place Savage.