The quake hit Yingjiang county under Dai-Jingpo autonomous prefecture of Dehong at 9:20 a.m., Xinhua quoted the China Earthquake Networks Centre as saying.
Tremors were strongly felt in the county, where residents rushed to open areas.
Of the 150,000 residents in 15 townships affected, 35,000 have been relocated to safety zones, said Wang Junqiang, the Communist Party chief of Dehong prefecture.
Even though the quake had a higher magnitude compared to one a week ago, it did not cause much loss as local authorities had warned of aftershocks and secondary disasters and evacuated residents from damaged buildings, said Wang.
The Yunnan government has initiated a grade II emergency response, sending a work team of over 50 people for surveying, investigation and disaster evaluation.
More than 3,500 soldiers, paramilitary officers and policemen are involved in the rescue work.
The epicentre of the quake was at Kachang township.
Yingjiang borders Myanmar and has a population of 300,000. In March 2011, the county was jolted by a 5.8-magnitude quake, leaving 26 people dead and over 300 others injured.