Theoretical and experimental study of passively mode-locked Nd³⁺∶YAG laser is reported. Light intensity in cavity that changes with the rotation of corner cube is analyzed and the numerical simulation results are provided. By using polarization,pulse output of linear polarization state is obtained. By rotating the corner cube to vary the polarization and the intensity in cavity,we can change the pulse state from passive mode-locking to Q-switching. It is in agreement with theoretical analysis.