Abstract: As the developing of MEMS（micro electromechanical system）,micropower becomes a very key problem in MEMS application gradually.The paper accounts simultaneously for the choice and decay type of isotope,particle energy spectrum,the energy loss rate of emitted particle in the mass,semiconductor characteristic and generation and recombination of carriers and sets up a theoretical model of radioisotope microbattery based on β-radio-voltaic effect.The model can calculate short circuit current and open circuit voltage of microbattery.The simulated result is slightly bigger than literature results;doped density of diffu-sion layer,the diffusion depth and radiation particle activity respectively influences export parameters of bat-tery.The model is considerably instructional and useful for developing microbattery.