This paper presents the simulation system of gravity gradiometer of rotating accelerometer and, according to the working principle of gravity gradiometer of rotating accelerometer, puts forward the method for gravity gradient signal simulation. The process of simulating gravity gradient signal is as follows: digit signals of accelerometers are produced by computer and gravity gradient is obtained through digit and analog conversion, analog operation, amplification, filter, analog and digit conversion, and modulation. By using this simulation method, the signal characteristics, parameter adjustment, error compensation and signal processing method can be further studied, and the results can serve as references for gravity gradiometer instrument design and development.