Abstract: The numerical model of the light field distribution in the side-pumped laser medium of LD was established. An analytical solution for the pumping light refraction in the rod-shaped gain medium was simplified with ray tracing. The normalized distribution of pumping light in the medium was simulated numerically with Matlab. The selection principle to acquire the parameters of high-quality and high-energy laser output is proposed. The influence of the structural parameters on the distribution of pumping light is analyzed. The experiment result shows that the gain distribution of pumping light in the laser medium is satisfactory when the radius of the beam waist is 1μm, the number of LD is 40, the radius of the medium is 1.5mm, the pumping distance between the luminous surface and the medium is 0.5mm and the absorption coefficient of the medium is 2cm-1 ～6cm-1.