Almost 200 people were killed in the unrest, according to Chinese state media, which said most of the dead were ethnic Han Chinese killed by Uighur rioters.
The ethnicity of those sentenced on Monday was not reported, although all appeared to have Uighur names.
The convictions are the first to be reported since the July 5 riots which broke out following street protests against attacks on Uighur workers at a toy factory in southern China in June that left two Uighurs dead.
Urumqi has been under extremely heavy security since the July riots, with armed police manning road blocks and patrolling the streets.
According to earlier reports police have detained more than 700 people suspected of crimes related to the riots, although how many will face prosecution remains unclear.