The Guangzhou schoolboy followed up his first round five-over-par 77 with a 79 at par-72 Tianjin Binhai Lake Golf Club. Guan was tied 150th out of 155 players in the $3 million event co-sanctioned by OneAsia.
Guan had already made history just by teeing off in Tianjin at the age of 13 years and 177 days. The youngest cut-maker on the European Tour is Jason Hak, who reached the weekend at the 2008 Hong Kong Open aged 14 years and 304 days.
The story of the slight Guan, who started playing aged four and won the world junior title by 11 shots last year in San Diego, has outshone some of the big names taking part in Tianjin including Ian Poulter and Paul Casey.
Guan, who also has hopes of reaching this year's US Open through qualifying, received a last-minute entry to the tournament via the China Golf Association.
"Long term, I was the youngest player to win the China amateur championship and it would be nice to be the youngest to win the (Volvo China) Open," he said this week.
After two rounds England's Gary Boyd and Jean-Baptiste Gonnet of France shared the lead with 11-under-par totals of 133.
"It was good today because the conditions were tough," Boyd said afterwards, according to a OneAsia statement. "It was cold and windy out there so it makes the score all the more satisfying."
He credited a return to his old coach for his good form, after had tried unsuccessfully to tinker with his game.
"There wasn't a lot wrong there but this is such a mental game that if the confidence slips a little bit it can just start to multiply the problems pretty quickly and all of a sudden you are down on yourself."
The Frenchman Gonnet also stressed keeping things simple, even under pressure.
"I have to go back to the five year old kid and try to play for fun. That will be the main aim for the weekend -- to go out there and try to enjoy it because there is no point in playing the game if you are not having fun."
England's Poulter closed with birdie, birdie for a 71, scraping over the cut by a single shot, and Colin Montgomerie was seven strokes off the lead. But Casey, who has struggled with injury, missed the cut at three-over-par 147.
Leading scores after the second round (A denotes amateur):
133 - Gary Boyd (ENG) 66-67, Jean-Baptiste Gonnet (FRA) 66-67
134 - Branden Grace (RSA) 67-67
135 - Nicolas Colsaerts (BEL) 68-67
136 - Choi Jin-Ho (KOR) 69-67, Marcus Fraser (AUS) 67-69, Ignacio Garrido (ESP) 67-69
Selected:
140 - Colin Montgomerie (SCO) 68-72
142 - Ian Poulter (ENG) 71-71
147 - Paul Casey (ENG) 68-79
156 - Guan Tianlang (CHN - A) 77-79