The accurate water vapor can be estimated by Global Navigation Satellite System, it also can be successfully applied to weather forecasts, such as numerical weather prediction models. The paper uses precise point positioning technology to retrieve the zenith tropospheric delay, retrieving the zenith tropospheric delay from the precise point positioning module in RTKLIB. Compares with the reference value provided by IGS to evaluate its accuracy of tropospheric resolution. The observation data of three IGS stations in China are selected for experiment, and the results show that RTKLIB can obtain the cm-level accuracy of the zenith tropospheric delay.