Taking the involute spur gear pair as the research object,the tooth surface convection heat transfer equation is obtained based on the improved friction heat spread by centrifugal ejection model,the tooth surface heat flow equation is obtained based on finite element method and friction heat analysis,on this basis,the gear pair bulk temperature is analyzed considering axis parallelism deviation. Then,thermal- structural coupled model is established,thus gear modification amount is analyzed under axis parallelism deviation and gear pair bulk temperature. After that,the method of calculating appropriate amount of modification is obtained. The result shows that the modification amount can be affected by temperature,and axis parallelism deviation may cause different axial mesh in / mesh out interference,gear pair with axis parallelism deviation is suggested to use profile and axial modification.