Abstract: To investigate the thermal loss characteristics of the parabolic trough loops using molten salt as heat transfer fluid at night,the steady-state heat transfer model for the typical trough collector was established based on the energy balance and thermal resistance model. Good agreement was obtained between numerical results and experimental data,validating the applicability and accuracy of the model developed. On this basis,the effects of loop length,ambient temperature,wind velocity,molten salt velocity,molten salt inlet temperature and the vacuum level on thermal loss were systematically analyzed. Results indicated that,during the night condition,the loop length,molten salt velocity,molten salt inlet temperature and vacuum level are main influence factors for thermal loss performance. By contrast,the ambient temperature and wind speed have little influence.