Abstract: Abstract: In this paper, a test device of solar membrane desalination system through distillation is designed in order to optimize the running process of solar membrane desalination system through distillation. The device uses photovoltaic-thermal system instead of conventional power to drive the power load during the running process of the system. The best operation condition is determined by means of test. The running performance of the system is tested in Hohhot, Inner Mongolia Autonomous Region, under the optimized circulation flow circumstance; the optimal heat flow rate is determined, the running effect of membrane desalination system in the best condition is tested, and the power balance of the system during the operation is illustrated. During the test outside, the average daily temperature is 21.78 ℃, the average wind speed is 2.94 m/s, and the main wind direction is northwest. The results show that there is a best endothermic circulation flow rate, which makes the total heat absorption decrease if it is too small or too large. The best circulation flow rate of solar thermal and photovoltaic system is 150 L/h. Corresponding temperature of the heat water increases by 2.5 ℃, which is the maximum value under all the circulation flow rates. The amount of heat absorbed by the heat exchanger in the unit time is the largest; the solar thermal and photovoltaic system should adopt the continuous track to run. After the incident angle of the sun’s rays is greater than 20°, the heating rate of solar collector sharply declines and the temperature rise values at measuring points are close to 0 ℃. In the heating process, there are 3 kinds of control methods. When the irradiance is less than 500 W/m2, only the photovoltaic system is opened to heat the working medium; when the irradiance is 500-700 W/m2, the thermal and photovoltaic complementary mode is used to heat the working medium; when the irradiance is greater than 700 W/m2, the thermal system opens to heat the working medium. With the good thermal insulating performance of hot water tank, system runs efficiently. The average flux is 14.92 kg/(m2•h) after optimization. The single membrane area is 0.01 m2. The average human intake of water is 2.5 kg/d, and 10.44 kg water can be produced by 0.14 m2 hydrophobic membrane which runs for 5 h in the optimized conditions. Seven groups of membrane modules in series can meet the drinking water needs of a family of four. The power consumption of electric heating is much larger than the total power consumption of 3 pumps. The power consumption during the whole test is 2.61 kW•h. The DC (direct current) meter shows that the average electrical energy generation by photovoltaic system is 2.4 (kW•h)/d. The membrane desalination system runs 5 h/d, which meets the demand of the photovoltaic system. The balance of electric power is maintained in the process of system operation. At last, this research can determine the minimum membrane area that per unit water production requires, get the maximum water production with the minimum initial investment, and promote the practical application of the membrane desalination system. The results provide a reference for the application of membrane distillation for desalination.