In the vertical integrated observation research and experiment for the metropolitan cities,the ECMWF reanalysis data are analyzed to evaluate the precipitable water vapor(PWV)observations of GNSS/MET,radiosonde,and water vapor radiometer(WVR)at the Beijing Observatory in 2018. Our results show that the correlation coefficients are as much as 0.90 with the ECMWF reanalysis. The PWV biases of the GNSS,the radiosonde and the WVR to the ECMWF are 0.54mm,1.94mm,-0.65mm respectively. The RMSEs are 3.55mm、3.60mm、6.08mm respectively. In comparison with the radiosonde,the biases of the GNSS,the ECMWF and the WVR are -1.39mm、-1.94mm、-2.58mm,and the PWV RMSEs are 2.85mm,3.59mm,6.79mm,respectively. It suggests that GNSS/MET PWV is of relatively high quality,perfectly matching with the radiosonde and the ECMWF,whereas the WVR PWV is of relatively poor quality. When data of rainy days are removed,the quality is improved both in bias and in RMSE for the WVR. It implies that the limitation of the WVR in its application,and further research on the retrieval algorithm of the WVR is needed in the future.