Abstract In this paper, we propose a zenith tropospheric delay interpolation algorithm based on vertical profile function by analyzing the law of zenith tropospheric total delay (ZTD) with elevation variation derived from ERA-Interim reanalysis data. Based on the vertical distribution law of ZTD, this method can realize accurate projection and extension of tropospheric delay on the elevation direction by vertical profile function. Compared with the traditional interpolation algorithm, the spatial structure malformation caused by the large elevation differences can be avoided. An experiment is performed with the tropospheric delay products of IGS, and the results show that the proposed algorithm can effectively improve the accuracy of ZTD correction value compared with the traditional algorithm. Especially in the case of elevation difference over 1 km, compared with the inverse distance weighting method, the accuracy is improved by 96%, which is 79% higher than the spatial regression method.