In the present paper, we analyze the influence of surface effect on the nonlinear bending behavior of piezoelectric nanobeams by Euler-Bernoulli model and surface energy model. Based on the principle of minimum potential energy and the electromagnetic theory, the nonlinear governing equation as well as the boundary conditions is deducted incorporated surface effects and piezoelectric effects. The effect of surface effect on bending deformation and induced charge of piezoelectric beams under different boundary conditions is discussed under the condition of small deformation and large deformation. The results show that, under the condition of small deformation, the surface effect reduces the bending deformation and the inductive charge, under the condition of large deformation, the surface effect has little effect on the bending deformation of piezoelectric nanobeams. Furthermore, the external constraints and cross-section width b of the piezoelectric nanobeam have significant effect on the bending deformation stiffness. these conclusions have important guiding significance for the design and correction of nanobeams-based nanomechanical systems and piezoelectric nanofunctional devices.