Abstract: The resonator for two rods Nd:YAG laser have been investigated by means of matrix Optics .Influence of differences of thermal lens focus on beam of two rods solid-state laser has been analyzed. The results show that the total mode volume is bigger than others when the mode volume of the two rods are equal. In mode matching state, the mode volume and the facula radius are further improved,and the quality of the output beam has also been improved.