The tunneling effect is a kind of quantum effect used extensively. The sensor based on tunneling effect has some advantages, such as high sensitivity, rapid response, low power consumption, low driving voltage and so on. In particular, combined with the MEMS technology, tunneling effect has shown a good application foreground in micro sensor fields. According to the quantum mechanics, such as Schordinger's equation, the theory models of tunneling effect are presented in this paper. Also the expressions of the transmission coefficient and tunneling current about the tunneling barriers are obtained. On the basis of these, a kind of MEMS micro magnetometer based on tunneling effect is presented. The mechanics model of the membrane, which is the key component and is subjected to the axial residual stress at both ends, is founded. The membrane's parameters are optimized and simulated. Some key fabrication processes of the micro magnetometer, such as silicon wafer, glass, combined plate process are developed. Further more, the prototype ofthe MEMS micro magnetometer based on tunneling effect is fabricated.