The 17-year-old fired a total score of 499.5 to beat South Korean Go Do Won, 15, by 0.9 in the Asian Youth Games girls' air rifle event on Wednesday.
Kuwait's Hessah Alzayed, 16, was a further 0.8 behind as she claimed the bronze.
It was a see-saw battle for top honours with the lead changing several times in the eight-woman final shoot-off at Safra Yishun.
But Chunchan maintained her patience and concentration to prevail. The Jiangsu native said: 'Shooting is very unpredictable. I just tried to keep a clear mind and not focus on the other scores.'
Singapore's Jodie Tan, 17, made the shoot-off but could manage only a 496.3 total for fifth place.
She admitted: 'I got a bit nervous at the end and it's a shame. I was quite close to getting a medal.'
The Republic's other representative Goh Jia Yi, 14, finished ninth in the 33-strong field, a result which she described as 'disappointing'.
