Chinese media reported that about 20,000 houses were damaged.
Sixteen aftershocks, one of them measuring 5.6, also shook Yiliang County in Yunnan.
The death toll is expected to rise.
In 2008, tens of thousands of people were killed in an 8.0 magnitude quake in China.
At least 50 people have been killed and dozens of others injured in a series of earthquakes in southwestern China, the state TV says.
The largest tremor, measuring 5.7 on the Richter scale, took place at 11:19 a.m. local time (0319 GMT) on Friday, jolting the mountainous area between the provinces of Yunnan and Guizhou.
The China Earthquake Networks Center (CENC) said the quake occurred at the depth of 14 kilometers (9 miles).