Abstract: The coordinate system transformation between the WGS-84 coordinate system and geodetic coordinate system in GPS is the three dimensional small angular region rectangular coordinates transformation. We researched on the serviceability of weighted total least-squares method, the LS-TLS method and the least-squares method in the three dimensional small angular region rectangular coordinates transformation. We found that when the coordinate observed value was influenced by the error in both of the coordinate systems, using WTLS method could revise the observation vector y and the coefficient matrix A, introduce the coordinate prior precision to the adjustment computation, and fix the constant element and adjust the data element through with the weighted matrix PA.This would make the model to be more precise and more reasonable and obtain the high accuracy parameter solution.