Metal-oxide based Resistive Random-Access-Memory (RRAM) exhibits multiple resistance states, due to the growth and retraction of a conductive filament between the electrodes of the device. The performance of RRAM relies on the fast switching speed, large current on/off ratio, and longer endurance reliability, which are critically dependent on the nonlinear resistive switching under electrical bias, temperature, interfacial chemical reaction and mechanical stress effects. In this work we developed a comprehensive phase-field model to simulate the resistive switching. The developed model enables us to separately study the aforementioned effects and understand their relative roles in the switching process. By choosing TaO_x as an example, we find that voltage-driven ion transport is responsible for the resistance change between low and high states. It also induces a local stress that influences the endurance of the device. Our work helps shed light on understanding the microstructure dependent ion transport behaviors in RRAMs.