Abstract: The preliminary analysis of the atmospheric water vapor detection performance of Beidou-3 global satellite navigation system (BDS-3), which has just been deployed in China, can make better use of the meteorological detection potential of BDS-3. In this paper several methods are compared using data from diffent stations around the world. The results are representative and convincing. The results of the study showed, comparing BDS-3/PWV with GPS/PWV, the average deviation (BIAS) was preferable to 1.0 mm, the root mean square error (RMSE) was better than 2.0 mm, and the correlation coefficients were all above 94%; The mean of the absolute values of the difference between of BDS-3/PWV and GPS/PWV (MEAN) was 1.1 mm, which was 71% lower than BDS-2; The RMSE of BDS-3/PWV and GPS/PWV was 1.4 mm, which was 63% lower than BDS-2. Comparing BDS-3/PWV with ERA5/PWV, BIAS was preferable to 2.9 mm, RMSE was better than 2.8 mm, and the correlation coefficient was above 92%. The MEAN of BDS-3/PWV and ERA5/PWV was 2.1 mm, which was better than BDS-2 reduced by 48%; The RMSE of BDS-3/PWV and ERA5/PWV was 1.6 mm, which was 57% lower than BDS-2. The water vapor detection performance of BDS-3 was much better than BDS-2, which was in good agreement with GPS and ERA5 water vapor detection results.