Abstract: With the rapid development of GNSS,especially for COMPASS and regional CORS station,how to use these abundant GNSS signals to tomography spatial water vapor becomes one of research focuses.It is necessary to use additional constrained condition for tomography spatial water vapor.In order to get reasonable weight for different observations and reduce atmosphere effect for lower elevation GPS signals,the tomography algorithm with robust variance components estimation(R-VCE) is detailed researched and analyzed in this paper.The results indicate that the algorithm with R-VCE is reliable for Ground-based GPS tomography water vapor.