Based on precipitable water vapor retrieved from ground-based GPS,data of ground automatic meteorological stations and conventional weather data,the evolution tendency of precipitable water vapor and ground pseudo-equivalent temperature during a heavy rain in south central Hebei province is studied.The results show that the heavy rainfall are caused by warm-wet flowing and shear line at the edge of subtropical high,and the precipitation area is between 584 to 588 dagpm lines in 500 hPa,between shear line in 700 to 850 hPa.Rainfall usually occurs when the GPS-retrieved precipitable water vapor is higher than the average value,especially near its maximum value,and the heavy rain period is corresponding to the maximum value stage of precipitable water vapor.Rainfall occurred more often when the deviation coefficient of GPS-retrieved precipitable water vapor is positive,heavy rainfall generally happens while deviation coefficient is higher than 1.For the same station,when GPS-retrieved precipitable water vapor is high,the real precipitation is strong.While for the different stations,the high precipitation is not necessarily represent strong real rainfall,for it is corresponding to the station location and altitude.High-energy accumulation is a necessary condition of rainfall.The rainfall of subtropical high usually occurs in the rapid decline phase of pseudo-equivalent temperature or its valley areas.The precipitation will be stronger when pseudo-equivalent temperature is at high peak,in sharp movement and with long duration of high value.