After the full use of CGCS2000 coordinate system, it is often necessary to batch convert plane rectangular coordinates such as Beijing 54 coordinates and local independent coordinates into CGCS2000 coordinates. Coordinate transformation is divided into indirect method and direct method. The indirect method takes geodetic coordinates (B, l) as indirect parameters and converts them according to the ellipsoidal projection principle. The theory is rigorous and the conversion is accurate. The direct method is to establish the coordinate transformation equations or numerical approximation model based on the least square method according to the regional common point coordinates. Orthomorphic transformation is one of the direct methods. It has the advantages of equiangular transformation and can be used in rectangular coordinate transformation of Gaussian projection plane of the same sphere and different spheres. In this paper, a simple nonlinear fitting global optimization method and multiple linear regression analysis method are used to solve the parameters of orthomorphic transformation, and the results are the same. The method of multiple linear regression analysis is simple, the calculation is fast, and the conversion accuracy is enough to meet the needs of engineering.