The unrest broke out after ethnic Uighurs attacked Han Chinese during streets protests against an earlier attack on Uighur workers at a factory in southern China that left two dead.
Thursday's sentences follow the executions of nine people last month for their roles in the riots.
The nine, who were believed to include ethnic Uighurs and at least one Han Chinese, were accused of committing murder and other crimes during the riots.
The death sentences and executions have been condemned by Uighur activists as politically-motivated, saying they will only serve to further aggravate Uighur grievances.
Energy-rich Xinjiang, strategically located in central Asia, has been struck in recent years by bombings, attacks and riots, which Beijing blames on Uighur separatists.
The estimated eight million Turkic-speaking Uighurs have long complained of religious, political and cultural oppression by Chinese authorities, and tensions have simmered in Xinjiang for years.
Many Uighurs also resent the massive influx of Han Chinese settlers who have in some areas reduced them to a minority in their own land.
Rights groups and Uighur activists have accused Beijing of grossly exaggerating the threat from separatists to justify harsh controls.