The inversion algorithm of pinion machine-tool machining parameter for spiral bevel gear is investigated.The pinion tooth surface equation of spiral bevel gear generated by modified-roll method is deduced,the least squares optimization model of the tooth surface is established in order to obtain predesigned target surface,and it is solved by using the levenberg-marquardt method with trust region strategy,and the generalized inverse matrix method and truncated singular value decomposition method are also used to identify the machine-tool machining parameter separately.A numerical example shows the effects of tooth surface approximation,according to the three algorithms,the sum of squared errors between the identified surface and target surface is followed by 1.472 3×10-3 mm2,8.296 9×10-4 mm2 and 1.499 3×10-5 mm2,the result reveals that the levenberg-marquardt algorithm can greatly improve the accuracy of the tooth surface approximation with respect to the first two methods.This iterative algorithm can be used for tooth surface deviation correction and active modification design of spiral bevel gear.