Tropospheric delay correction error is one of the important error sources of deep space interferometry. In this paper, a high-precision regional tropospheric delay model is constructed by modifying the classical tropospheric zenith delay model and Niell Mapping Function (NMF). Firstly, the applicability of Saastamoinen model was analyzed based on the tropospheric delay data measured at Kashi Deep Space Station of China's Deep Space Network. The zenith stem delay parameters were modified by linear least square fitting, and the model accuracy was improved by 29.6%. Then, aiming at the problem of large mapping deviation of NMF at low elevation angle, a deviation function model was constructed, which significantly improved the mapping performance at low elevation angle. The measured data verified that the tropospheric delay model deviation was relatively improved by about 30% when elevation angle was 0°~30°. The tropospheric regional model proposed in this paper has high estimation accuracy and can provide reference for tropospheric delay correction in deep space interferometry in China.