In this study, effect of different operating conditions on the performance of a solar assisted heat pump desalination system with humidification-dehumidification have been investigated experimentally, and the working principle of the system was described. An experimental setup that consists of a compressor, condenser, evaporator, PTC electrical heater, pad humidifier, fan, precooler and seawater tank was designed and fabricated to evaluate the influence of flow rate of cooling seawater and process air, seawater concentration and mixture ratio. And the performance of the unit including the productivity and thermal efficiency were obtained during the experiments. The results of the experimental study showed that the productivity of the system decreased with the increased of cooling seawater flow rate, and the fresh water production and thermal efficiency of the setup will first decreased then increased with the increase of the flow rate of cooling seawater. The maximum productivity and thermal efficiency of the unit is 12.38kg/(kW·h) and 0.807, respectively. The productivity of the system first increased then decreased with the increase of the process air flow rate, and the optimum flow rate of process air is 450m3/h. The optimum seawater concentration for maximum productivity of the unit is about 7%, and the influence of mixture ratio on the productivity is less than 2% for this desalination system when the mixture ratio is greater than 0.9.