The US Geological Survey said the 5.7 magnitude quake struck in Yunnan province at 1917 local time (1119 GMT).
It damaged 30,000 homes and was followed by eight aftershocks, Xinhua news agency reported.
The agency said authorities had sent thousands of tents, quilts and other aid materials to the site of the quake.
The epicentre was reported to be in a mountainous area in Yaoan County.
The 30 people who were seriously injured were being treated in hospital there, Xinhua said.
Hundreds of police have also been deployed to provide assistance, the agency said.
http://news.bbc.co.uk/2/hi/asia-pacific/8143503.stm