According to the parameters of the cutting tool and the basic parameters of the shaft blank when the spline shaft parts were cold rolled,the model was established;the numerical simulation of the cold rolling process of the spline shaft was carried out,and the simulated spline tooth profile was consistent with the actual situation.On this basis,the micro simulation parameters of the model were set to simulate the change of micro size in the machining process from the micro level.Because the material performance was related to the grain size,the changes of the micro grain size and quantity were taken as the index in the cold rolling forming process.The influences of friction coefficient,rolling speed and environmental temperature on the friction coefficient were investigated by orthogonal test.Through the range and variance analysis for three factors on the micro grain size of the material,it was concluded that the rolling speed had a significant effect on the grain size.