The Main Belt Comet 133P/Elst-Pizarro is one of the targets in China’s asteroid exploration mission. To support this goal, gravity field estimation for this celestial object was simulated and analyzed using two-way and four-way range rate observations. A circular terminator orbit was designed for the spacecraft, and the forces acting on it were modeled to estimate the related dynamic values. Various solutions using different tracking modes and different orbital distances were approximated using the least squares method, constrained by the currently known GM bounds of this comet. The simulation results showed that unlike the two-way range rate observables, the four-way range rate observables are found to be able to reduce the correlations between the gravity field coefficients therefore decrease their uncertainties, especially in lower degrees.