Abstract: In order to improve the beam quality and spectral characteristics of a high power double clad fiber laser and improve the stability of the optical fiber system, a novel high power cladding light stripper was designed to strip the residualoptical power in the fiber cladding. High power cladding light stripper was analyzed through theoretical calculation and simulation analysis. Based on the Monte Carlo algorithm and light trajectory tracking method, the performance of the cladding light stripper was calculated. With the aid of computational fluid dynamics software ANSYS, the temperature field distribution of the cladding light stripper was analyzed. After optimizing the cascade model structure, strip efficiency of the stripper can reach up to 16.7dB, the hot-spot temperature of the cladding light stripper was reduced, and uniform strip was realized, hot-spot temperature was decreased 20.8℃ under the input power of 600W. The results show that the cladding light stripper can work stably at 70℃ when the power reaches the kilowatt level, it can meet the requirements of high power fiber laser systems.