Abstract:  From the perspective of the practical application of ground-based GPS meteorology, it is a critical problem to obtain the atmospheric water vapor field of high spatial and temporal resolution in real time. Based on the principle of ground GPS water vapor remote sensing using Hong Kong CORS network of actual measuring data, according to the different precision of the orbit of IGS web site provides information design the experiment scheme, this paper compares the schemes of precise ephemeris, eventually ultra-rapid ephemeris and meteorological sounding station PWV sequence detection. The results show that the predicted PWV data of the ultra-rapid ephemeris agree with those of the final precise ephemeris, and its accuracy can meet the real-time business needs, such as weather forecasting.