This paper aims at predicting radiation characteristics of the solar collector system by the Monte Carlo method with respect to the corresponding optical properties. Several probability models were introduced to analyze the effects of sunshape and surface roughness. Directional characteristics of radiative flux in the focal region and flux distribution of the cavity receiver were considered. An equivalent radiation flux method is presented for designing the shape of the cavity receiver. Based on the relative numerical simulation results, a new shape cavity receiver called “upside-down tear drop” is proposed to meet an almost uniform radiation flux field. Radiation effects due to multiple reflections and thermal emission in the cavity are parametrized by using the radiative exchange factor. The calculation results can be a valuable reference for the design and assemblage of the dish solar collector system.