Abstract：This paper uses GPS water vapor retrieval and GPS-interferometric reflectometry (GPS-IR) technology for precipitation analysis and judgment. First, considering that before and after precipitation occurs, and that atmospheric water vapor content, ground reflection characteristics, GPS tropospheric delay, and signal-to-noise ratio (SNR) amplitude (A) will change, we analyze the correlation between GPS-PWV/SNR-A and precipitation, and combine the two to determine precipitation. The results show that precipitation is positively correlated with GPS-PWV and negatively correlated with SNR-A. The addition of SNR-A data can improve the forecast rate and accuracy for precipitation judgment. Based on the troughs of SNR-A sequence and the peaks of GPS-PWV sequence, in this work the forecast rate of precipitation judgment is about 70%-82% and the accuracy rate of precipitation judgment is about 50%-60%.