Summer rainstorms occur frequently in Beijing-Tianjin-Hebei region.As one of the key factors affecting the formation of heavy rain,precipitable water vapor has been recognized as highly correlated with the Global Navigation Satellite Systems Zenith Tropospheric Delay(GNSS ZTD).In this study,the time series of GNSS ZTD and their response to El Niño events were analyzed based on GNSS observations in Beijing-Tianjin-Hebei region.Fast Fourier transform and wavelet transform were used to carry out GNSS ZTD timing sequence analysis from frequency domain and time domain,and the time sequence of GNSS ZTD with different periodicity was compared with the Eastern-Pacific types of El Niño index(I_EP) and the Central-Pacific types of El Niño index(I_CP).The results showed that there was a corresponding relationship between the abnormal period of GNSS ZTD and El Niño events.Specifically,the GNSS ZTD was positively correlated with I_EP,and significantly negatively correlated with I_CP.Under the influence of I_EP,the GNSS ZTD increased in seasonal cycle,but decreased in monthly cycle and half-monthly cycle.While under the influence of I_CP,the GNSS ZTD decreased in seasonal cycle,monthly cycle,and half-monthly cycle.The above results can provide reference for regional GNSS ZTD variation analysis,and provide a reliable basis for sensing El Niño events with precipitable water vapor.