The nonlinear pull in behavior of piezoelectric laminated micro beam was studied with consideration of the size effect and damage effect. Based on the theories of continuum mechanics and Euler Bernoulli beam hypothesis, the nonlinear governing equation of piezoelectric laminated micro beam with damage was established and solved in Galerkin method and Runge Kutta method. The influence of various parameters on the pull in voltage of the micro beam was discussed, and the results have shown that the geometry nonlinearity can improve the value of critical pull in voltage of the micro beam; the changes of governing voltage, micro beam length and other parameters have influences on the critical pull in voltage of the micro beam. Besides，the FEM software was used to carry out the check up calculations, and the results were compared with the theoretical results. The findings of this research can offer guidance to the design of micro structures.