The temblor struck the border area between the provinces of Yunnan and Sichuan at 8:04 a.m. local time, the Chinese news agency Xinhua reported.
Some 9,200 people in the province were forced to relocate after the quake destroyed 600 homes and damaged 55,000 others, the Yunnan Provincial Civil Affairs Department said.
The epicenter was near Xingfu Village in Nixi Township in Yunnan's Shangi-La County. Landslides triggered by the quake cut off traffic to that area.
Telecommunications and electricity in Deqen County in Yunnan and Derong County in Sichuan have been damaged.
On Wednesday, a 5.1 magnitude quake rattled the same area, affecting more than 52,000 residents in Yunnan.