The US Geological Survey said the quake struck at a depth of 20km (12 miles) northeast of the city of Hotan, followed by a series of aftershocks.
Officials said more than 3,000 houses and buildings in the mainly ethnic Uighur region were damaged.
China is regularly hit by earthquakes, particularly in Sichuan and Yunnan.
"Buildings were trembling and people rushed to the streets," said Hotan resident Jin Xingchang.
The government said it would send 1,000 tents and other relief materials to the area, said AFP news agency citing the Xinjiang Bureau of Civil Affairs.
In 2008, a 7.9 magnitude quake rocked Sichuan killing more than 80,000 people, making it the worst earthquake to hit China for more than three decades.
At least four people have been killed and more than 48 injured by a magnitude 6.4 earthquake in China's Xinjiang region, according to state media.