The portable rainfall calibrator with the advantages of compact structure and portability is designed for regional automatic meteorological stations especially. Taking into account the thermal expansion, chemical stability, cost and machinability of the material, copper was chosen to make the screw that can control the precipitation intensity, and verification experiments are conducted. The performance evaluation test of copper in high temperature and low temperature has proved that the material can meet the requirement of the work performance. The selfdeveloped data processing software system adopts the C/S architecture to design hierarchically, which is powerful, can automatically record, process, and generate chart reports, and can judge the current detection status according to the realtime spectrum.