Urumqi labor dispatching social security payment

According to the Interim Provisions on Labor Dispatch

Article 8 A labor dispatch unit shall perform the following obligations to the dispatched workers:

(four) in accordance with the provisions of the state and the labor dispatch agreement, pay social insurance premiums for the dispatched workers according to law, and go through the relevant procedures of social insurance;

Article 18 Where a labor dispatch unit dispatches laborers across regions, it shall participate in social insurance for the dispatched laborers in the place where the employing unit is located, pay social insurance premiums in accordance with the regulations of the place where the employing unit is located, and the dispatched laborers shall enjoy social insurance benefits in accordance with state regulations.

Article 19 Where a labor dispatch unit establishes a branch in the place where the employing unit is located, the branch shall go through the insurance formalities for the dispatched workers and pay social insurance premiums.

If the labor dispatch unit fails to set up a branch in the place where the employer is located, the employer shall handle the insurance formalities for the dispatched workers on behalf of the labor dispatch unit and pay social insurance premiums.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.