Abstract: A ray tracing model is established based on the Monte Carlo method,and a CCD camera and a Lambertian plate are used to carry out the concentrated flux experiment. The experimental results show that the measured and the simulated spots are in good agreement in size,shape and flux distribution. A photothermal coupling model is proposed for the cavity receiver. Considering the radiation heat transfer between different heat absorbing tubes in the cavity,the maximum relative error between the simulation results and the experimental results is 8.6%.