Differential steering based on tire cornering suited low-speed, large steering radius scenarios of distributed drive electric vehicles(DDEV) without steering mechanisms. In order to study the mechanism of differential steering based on tire cornering, a 7-degree-of-freedom DDEV dynamic model with no steering mechanism and PAC2002 tire model were established. Then, the formation mechanism of differential steering was analyzed and a systematic analysis method from the input of differential longitudinal force to the output of vehicle steering radius of differential steering was proposed by considering the tire force longitudinal-lateral-coupling characteristics. Leveraging the proposed systematic analysis method, the stability of differential steering and the influences of differential longitudinal force, vehicle parameters and tire characteristics on steering radius were studied. Finally, a Carsim/Simulink joint simulation platform was established to simulate differential steering under different influencing factors. The results show that within the range of tire cornering, the larger the differential longitudinal force, the larger the ratio of track width to wheelbase, and the smaller the tire lateral stiffness, the smaller the steering radius.