Tensions between the region's minority Uighurs and majority Han Chinese turned deadly in Urumqi last July 5.
The government says nearly 200 people were killed and about 1,700 injured in the unrest, with Han making up most of the victims.
China has blamed ethnic separatists and Muslim extremists for stoking unrest in Xinjiang over the past decade.
Xinjiang, a vast, arid but resource-rich region that borders Central Asia, has more than eight million Uighurs, and many are unhappy with what they say has been decades of repressive communist rule by Beijing.
Many also complain about an influx of Han Chinese – China's main ethnic group – that they say leaves them economically and culturally marginalised in their homeland.