Saturday's quake struck about 50km southeast of Panzhihua city in the southwestern corner of Sichuan province.
It killed 27 people in Sichuan and five in the neighbouring province of Yunnan, the official Xinhua news agency said early on Monday, citing the civil affairs ministry.
Hundreds of people were injured and the quake also damaged major bridges and cracked three reservoirs, the agency said.
About 150,000 people were evacuated from the area but relief efforts were being hampered by heavy rains and the region's rugged terrain.
Xinhua said relief workers were trying to send tents, blankets and rice to the quake zone.