Abstract: For reverse calculation of the parameters of an involute-center and radius of basic circle,without knowing the center point of basic circle of the involute,this paper proposes a method as utilizing principles of Three-Point-Circle to calculate the initial values of objective parameters first and optimizing it by solving the non-linear least squares with Gauss-Newton method(GN method),and draws conclusion that this method can be applied to calculate the parameters of an involute and multi involutes,and also receives good effect when it is utilized to determine the initial coordinate value of probe in Gear Measuring Center.