Two policemen were also injured in the attack on the police station in Serikbuya Township of Bachu County in Kashgar Prefecture.
The nine assailants, including one identified as Abla Ehet, were armed with knives and axes, state-run Xinhua quoted local police as saying.
The restive Xinjiang province faced unrest between Uyghurs and members of Han community over the increasing settlements of Hans in the province.
China blames East Turkestan Islamic Movement (ETIM), fighting for independence of Xinjiang, for the violence.