In order to improve the machining accuracy of spiral bevel gear, an optimal design method based on biorthogonal B-spline wavelet was proposed. Based on the formation theory of spherical involute, the discrete point data of tooth surface were obtained by using MATLAB. The high-frequency detailed feature information of tooth surface was removed by using biorthogonal B-spline wavelet, and the main feature information of low-frequency main body was retained, and a set of more reasonable and effective discrete points of tooth surface were reconstructed. The reconstructed data points were accurately fitted through NURBS surface, the tooth surface with lower Gaussian curvature and lower complexity was obtained. The digital model of the tooth surface obtained by using this method was processed by numerical control, and the precision machined tooth surface was measured and the error was analyzed by using coordinate measuring instrument. The results show that the tooth surface processed by biorthogonal B-spline wavelet has high machining accuracy; a new theoretical method is provided for improving the machining accuracy of spiral bevel gear by reconstructing the digital model of spiral bevel gear.