The initial quake was quickly followed by two aftershocks of magnitude 5.1 and 5.2, both roughly in the same location Chinese seismologists said.
Reports from the area say there has been some damage to villages, but there is no indication as yet of any casualties.
Local officials told the AFP news agency that assessment teams had been sent out to survey for damage, but the operation would take time because they are having to travel on horseback or foot in areas with few roads.
The region is seismically active but Xinjiang is a relatively sparsely populated area.
China's deadliest earthquake in recent history struck the northeastern city of Tangshan in 1976, killing an estimated 240,000 people.
Its magnitude was measured at 7.8 to 8.2.