Disclosed are a mobile terminal and a service processing method thereof, and a baseband processing chip are disclosed in the embodiments of this invention, wherein the service processing method of the mobile terminal comprises: in response to the situation that a first user card in an on-network state is required to process a high real time service, identifying whether PS domain data being received/transmitted in a PS domain service currently processed on a second user card is the critical data for maintaining the QoS level of the PS domain service, wherein the high real time service has higher requirement to real-time than the PS domain service, and the first user card and the second user card belong to the multiple user-cards inserted in the same mobile terminal; in response to the PS domain data being received/transmitted is non-critical data, suspending the processing of the PS domain service and processing the high real time service. Embodiments of this invention allow a multi-card multi-standby mobile terminal based on a single RF single baseband scheme to process a high real time service on other user cards during processing a PS domain service on a user card.