Abstract: Heat receiver is one of the key parts of the SDPS.It absorbs the solar flux and stores thermal energy.Since the surface temperatures of canisters are different,the reradiation in cavity will change the flux distribution on the tube outer surfaces,and the thermal emittance of the canister outer surfaces will affect heat receiver thermal performance significantly.The heat receiver cavity radiation mathematical model and the gas tube heat model were used for two values of surface thermal emittance to calculate heat loss,energy absorbed by gas,tube maximum temperature,gas exit temperature and liquid PCM fraction.The results obtained for these two values of emittance were compared and analysed between two surface thermal emittances.It is shown that higher surface thermal emittance is very important to improve the heat receiver thermal performance.