A new method of zenith troprosphericdelay modeling (HTIM) for sparse reference station network is put forward in this paper.The zenith tropospherichydrostatic delay (ZHD) is calculated by the UNB3m model.In addition,the zenith troposphericwet delay (ZWD) with high precision is estimated by conventional precise point positioning (PPP) using ionosphere-free combination.Considering the relationship between heightfactor and zenith tropospheric delay (ZTD) in UNB3m model,the zenith tropospheric delay is divided into two parts,the heightweakly correlated and the heightstrongly correlated.The new method of zenith tropospheric delay modeling isestablished using the two parts of the zenith tropospheric delay.Based on the results of regional modeling,the zenith tropospheric delay of rover station is augmented.The new method is compared with conventional modeling methods.The results show that the new zenith tropospheric delay modeling method is superior to other methods in the undulated region only using four reference stations,RMS is 0.020 meters and the absolute deviation is nearly within 0.03 meters.It also shows that the RMS is 0.008 meters and the rate of absolute deviation within 0.01m reaches 75.95% in the sparse reference station network.In the new method,the interpolation precision is not limited by the number of reference stations and three reference stations also can be used to get the interpolation results with high reliability.The results show that the new zenith tropospheric delay modeling method is superior to conventional methods,especially for the undulated region in a sparse reference station network.