Abstract: Based on the non-sequential mode ray tracing of Zemax, light intensity distributions of pumped face and end surface in composite slab were simulated respectively. The tracing results showed that the light intensity distribution was homogeneous when the pumping beam was on the pumped face, however, the light intensity distribution was non-homogeneous when it was on the end surface after transmitting through the undoped crystal. The investigation results indicated that the propagation of pumping beam in the undoped crystal caused total internal reflection, which induced the overlap of pumping beam in partial region of end surface, and then induced the non-homogeneity of pumping beam distribution on the end surface. Finally, according to the planar waveguide homogenization theory, we put forward feasible techniques based on changing the length of undoped crystal and the divergence of incident beam to improve the pumping beam homogeneity, and carried out the simulation validation.