In order to accurately estimate the tropospheric slant delay of the two-way troposphere time transfer system, the Hopfield zenith delay model and the CFA2.2 mapping function model which can estimate the tropospheric slant delay of satellite signals were analyzed and modified, and was accepted by the accurate estimation of slant delay caused by tropospheric scatter. The meteorologic data of three observation stations from 35°N to 37°N in 2010—2012 were selected to verify that the precision range of Hopfield model was less than 35 mm. Then, in order to calculate the tropospheric delay under different angle of incidence through modified model, three observation stations were distinguished by different baseline distance and the meteorologic data of those stations in 2012 were used. The day of year and the incident angle under maximum slant delay were also obtained. Results suggest that the max delay is 21.82 m to 35.45 m in a single way time transfer. In two-way time transfer, when the delay is counteracted by 90% or 95%, the time delay is 7.3 ns～11.7 ns or 3.6 ns～5.9 ns. 