Laser cavity is indispensable in solid-state laser pumped by flash-lamps,which focuses the pump light on laser rod more efficiently and evenly. To achieve high-energy output,it is necessary to consider optimizing laser cavities and increasing the pumping efficiency. Through the ray-tracing technique of Monte Carlo method and establishment of reasonable model,four-lamps cavity was researched in certain diameter of laser rod. The relationships between pumping efficiency and the ratio of elliptic major axis and minor axis(a/b) were obtained. Moreover,the relationships between pumping efficiency and diameter of flash-lamps were obtained in certain a/b. The a/b of supreme pumping efficiency was obtained in certain diameter of laser rod and flash-lamp. In addition,the relationship between pumping uniformity and ratio of elliptic major axis and minor axis(a/b) were obtained on the condition of certain diameter of laser rod and uncertain diameter of flash-lamps.