The 25-year-old fired a bogey-free eight-under-par 64 for a one-shot lead over England's Matt Wallace and Nino Bertasio of Italy at Topwin Golf and Country Club in Beijing.
Sweden's Alexander Bjork and Scott Vincent of Zimbabwe shared fourth, a further shot back.
But the day belonged to little-known Jin, who has only made the cut once on a European Tour event, back on his debut in 2012.
"I played really well today," he told europeantour.com. "I'm really happy with my form and I have to say I would give myself 100 marks for today's round.
"I've been relaxed coming into this week because I don't have too much expectation but I'll just keep playing one stroke at a time, one day at a time and see how it goes for me."
Last year's China Open winner, Alexander Levy of France, carded a three-under-par 69 for a share of 18th.
Levy is chasing back-to-back European Tour wins -- and eyeing a Ryder Cup spot on home soil -- after triumphing last week in Morocco.
Another home hope, the highly promising Li Haotong, was tied 33rd after his first-round 70.
Japan's Hideto Tanihara won himself a car after nailing a 197-yard hole-in-one at the 16th on the way to shooting a 72.