Geophone is a special purpose sensor which can translate the mechanical vibration into the electrical signal. Micro-Electro-Mechanical Systems (MEMS) digital geophone is the one of the most advanced geophones at present. This paper researches on the internal structure of MEMS digital geophone and its working principle, and then a close circuit system of MEMS digital geophone is build according to the performance analysis experiments. The simulation results show the effectiveness and feasibility of the build MEMS digital geophone's close circuit system.