Abstract In this study, a solar dish collector is considered with a rectangular cavity receiver. The investigated parameters were included the receiver aperture area (a 2 ), receiver tube diameter, cavity depth, inlet temperature and mass flow rate through the receiver. This cavity receiver is used as the heat source of the organic Rankine cycle (ORC). The ORC system is considered with R141b as the working fluid at the saturated condition. The main objective is the calculation of the optimum parameters for attaining the maximum overall thermal efficiency of the system. With the help of the receiver modeling techniques, the optimum aspect ratios of 54.25, 40.69, 32.56, 23.25 and 18.09 are identified for five cavity depths of 0.5a, 0.75a, 1a, 1.5a, and 2a where the accompanying optical efficiencies are 89%, 92%, 94%, 96% and 96%, respectively. It is concluded that for increasing the collector efficiency and overall thermal efficiency, a higher mass flow rate, and a lower inlet thermal oil inlet temperature are required. Also the results show that the optimum characteristic of the cavity for achieving highest collector efficiency and the highest overall thermal efficiency includes smaller tube diameter, lower inlet temperature of the working fluid, and the cavity depth of 1a.