Defending champion Fredrik Jacobson climbed into second place thanks to a second-round 65. He is at 7-under-par 133, one shot clear of Henrik Nystrom.
McEvoy opened his day with a birdie at the 12th, but stumbled to a bogey on the par-4 13th for the second straight round. This time he responded to birdie the 14th to get back to minus 9.
He settled down to reel off seven straight pars around the turn. The 24-year-old Englishman climbed to 10-under with a birdie at the par-4 fourth.
McEvoy faltered to his second bogey of the round at the seventh. He managed to extend his advantage back to three shots thanks to a birdie at the very next hole.
'It is very pleasing to find myself where I am,' said McEvoy, the medalist at the 2003 European Tour Qualifying School Tournament. 'I played good, solid golf today.
'I didn't hole as many putts as I did yesterday, but didn't really hit it in close enough to hole many putts. After such a low first round, it's nice to get a good steady round in, shoot a couple under and let everyone chase it.'
Jacobson got rolling with back-to-back birdies from the third at Hong Kong Golf Club. He carded his lone bogey of the day at the fifth and was able to atone for that error with a birdie at the ninth.
On the back side, the Swede moved to minus 5 with a birdie at the 12th. Jacobson rolled home his fifth birdie at the day at the par-3 15th and capped his round with a birdie at the last.
Nystrom carded a birdie and a bogey on the front nine, but ran off three straight birdies from the 11th. He posted another birdie on No. 17 to cap a 5-under 67.
'I had a poor year in 2003 but I'm hoping a return to Hong Kong will revive memories of finishing second here last year,' said Nystrom. 'I am striking the ball well and now hoping for a good weekend.'
Irishman Padraig Harrington leads a group of four players at 4-under-par 136. He is joined there by Peter Gustafsson, who fired a 6-under 64 Friday, Prayad Marksaeng and Hennie Otto.
Chris Gane and Rob Rashell each posted rounds of 3-under 67 to move into a tie for eighth at 3-under-par 137. That duo is joined at minus 3 by Darren Clarke, Adam Fraser, Christopher Hanell, Amandeep Johl and Steven O'Hara.
The cut line fell at 2-over-par 142 with 75 players advancing to the weekend.