Abstract: For precise orbit determination of deep space exploration, precision of traditional two-way range-rate model is limited by computers' word length, where the main error source is the simple differenciation of two subsequent Newtonian ranges(up-leg and down-leg) devided by the counting interval. So interplanetary two-way range-rate model is built up in this paper to compute these two necessary differences highy precisely. Of course, we give the formula of this new model and its detailed steps as well as necessary recursion formula of Chebyshev differential polynomial. The new model is implemented in Wuhan University deep-space orbit determination and gravity recovery system-WUDOGS and two scenarios of simulation are adopted to validate it from two aspects:precision of calculation values and initial orbit based on Mars express mission. Simulating results show that the new model can improve precision of calculation values by two orders of magnitude, and reduce extra numerical error during orbit determination, which can provide reference for orbit determination in long-distance deep space exploration of high precision in China.