The invention discloses a switching method and a system of mobile terminal network optimization. A network comprises a mobile network and a WiFi (Wireless Fidelity) network. The method comprises the following steps: Step 1, setting an application network authority list in a mobile terminal and setting respective network priorities of applications, and Step 2, detecting that the applications access to the network, acquiring names of the application, searching the network priorities in the network authority list, and connecting to the network according to the network priorities. According to the method and the system, the applications can be connected to the network according to the set priorities with the adoption of the application network authority list, so that normal running of the applications is ensured; each application is provided with a priority network; the two applications with the priority networks not communicated with each other can operate simultaneously; each application is set in advance in the network authority list; manual setting is not required during use; the time is saved; and the efficiency and user experience are improved.