The invention provides a system and method for screening user rate according to network loads. The method comprises the following steps of: sending current network loads to a PCSCF (Proxy Call Session Control Function) or a PCRF (Policy And Charging Rule Function) by a base station; and screening the user rate supported by the current network loads by the PCSCF or the PCRF according to the current network loads in the encoding and decoding negotiation process of a calling subscriber and a called subscriber. The invention can be used for controlling the rate of calls according to wireless network loads and reducing certain user rate requested by a user while considering service experience when the wireless network loads are heavier, thereby being convenient to access more users and reducing the call loss; and in addition, the invention does not influence the call establishing time.