Jacquelin stands at 7-under-par 135 after 36 holes and is two shots clear of Adam Blyth. The Australian carded a matching 67 to move into second at minus-5.
Andres Romero and Scott Hend also posted rounds of 67 and share third place at 4-under-par 138.
Scotland's Simon Yates fired a 5-under 66, the low round of the week so far, to jump from 41st place into fifth place at 3-under-par 139.
Jacquelin got off to a flying start at Shanghai Silport Golf Club. He opened on the back nine and birdied the 10th.
The Frenchman, whose lone tour win came at the 2005 Madrid Open, came right back with birdies on 11 and 12 to move to minus-6.
'When we started, it was dead calm,' said Jacquelin of the wind conditions. 'I was lucky enough to make three birdies at the start and I was playing really well.'
Jacquelin kept rolling as he birdied the 14th, then the 17th from 20 feet to get to eight-under. He climbed to 9 under as he birdied the fifth from 15 feet out.
However, trouble loomed down the stretch. The 32-year-old tripped to back-to- back bogeys from the seventh to slide back to minus-7.
'Like yesterday I made two bogeys at the end, but that is the game, especially on this course in these conditions,' admitted Jacquelin.
Blyth, playing in the last group of the afternoon wave, also started on the 10th tee. After three straight pars, he stumbled to a bogey on the par-4 13th.
The Australian bounced right back with birdies on each of the next three holes. Those birdies moved him to minus-3.
Around the turn, Blyth faltered with a bogey on the first for the second straight round, but turned it on down the stretch. He birdied the fifth and came right back with a birdie on the par-3 sixth.
Blyth moved within two of the lead courtesy of a birdie on the par-5 eighth, then parred the ninth, his last, to finish two back.
'Now, I want to enjoy the ride over the weekend,' Blyth stated. 'It's a nice position to be in, so I hope to have fun and stay positive, so we'll see how it goes.'
Markus Brier posted a 3-under 68 Friday to climb to 2-under-par 140. He stands alongside Christopher Hanell (70), Graeme McDowell (70) and Damien McGrane (69) in a tie for sixth place. Stephen Dodd, Richard Sterne, Richard Lee and Jean-Francois Lucquin are one stroke further back at minus-1.
Thomas Bjorn, the lone player in the field this week that played at the Masters last weekend, carded rounds of 70-72 and is tied for 14th at even-par.
Ming-Jie Huang, who shared the lead with Jacquelin after the opening round, stumbled to a five-over 76 and tumbled into a share of 25th at plus-two.
The cut line fell at 4-over-par 146. Of the 25 players from China who teed it up this week, six made the cut and 19 were sent packing. Ren Han, an 18- year-old amateur, was among those sticking around for the weekend.
Among those missing out on the weekend were Marcus Fraser, Andrew Marshall, Thaworn Wiratchant, Christian Cevaer, Marcel Siem and Barry Lane.