In this paper, the dynamics analysis of Micro bistable piezoelectric plate with proof mass is carried out, where the plate center is fixed but the quadrilateral is free. The scale effect is considered by using the strain gradient theory. Considering the coupling effect of force, electric and thermal, the nonlinear dynamic equation is established with the aid of the Von?Karman large deformation theory and the Hamilton principle. Firstly, by means of the eigenvalue method, the effect of temperature and voltage on its natural frequency and stability is explored under the condition of different internal length scale parameters and different piezoelectric layer area. Moreover, the nonlinear dynamic response of the system under different external excitation is studied. It is found that with the increase of the piezoelectric area, the more obvious coupling effect of force, electricity and heat, the influence on the system stability is increased significantly. Temperature and voltage can stimulate or restrain the vibration amplitude, which provides a theoretical basis for vibration control. Meanwhile, it is shown that the size effect has a great influence on the structural stiffness, which proves the necessity to considere the scale effect for the micro structure.