Conventional meteorologic radar cannot distinguish radar reflectivity and specific attenuation of rain. There is some principled error to measuring rain by it. A new method on inversing rain rate distribution along Earth-Space path by radar-satellite system is presented in this paper. A recurrent formula of specific attenuation of rain is derived. A radar-satellite system for measuring rain is given. The typical results of distribution of rainfall rate along Earth-Space path are measured by this system.