Water rushed into the Xujiaba Tianchi mine in Sinan county on Sunday afternoon when 80 miners were in the shaft, said Wu Ming, an official at the mine.
Forty-four workers got out safely, but the fate of the others was still not clear on Monday morning, he said.
"Right now we have five pumps working to evacuate the water. We still don't know how deep the water is," Wu said.
"At this time it is hard to say if those in the mine have a chance to survive."
So far no casualties have been reported.
The mine is a small township-run operation that is legally registered with the local provincial government, he added.
China's mining industry has been blighted by a spate of disasters in recent weeks, including the deaths of 166 people in Shaanxi province and 148 miners in Henan province, both from gas explosions.