Aiming at discontinuity and cusp problem of pitch curves for non-circular gear pairs,based on the closed condition of pitch curve and transmission ratio function for non-circular gear,modification model of pitch curve design defects for non-circular gear is established. A modification factor is introduced into modification model to avoid effectively discontinuity of pitch curve. Based on geometrical relationship between points lied in pitch curve and its osculating circle,modification models for concave cusp and convex cusp of pitch curve are established respectively. The points lied in osculating circle are considered as interpolation points,the tangency points between osculating circle and pitch curve is boundary conditions of spline interpolation,cusp of pitch curve is modified by using numerical interpolation method. The results indicate that design deficiency such as pitch curve for high-order Achimedean spiral gear pair can be amended quickly by the algorithm,while it is exactly.