A novel Four-stage cross flow humidification and dehumidification (HDH) solar desalination system with direct contact dehumidifiers was proposed in this paper. Firstly, the composition and operation principle of the system were introduced. Then, the heat and mass exchange models of main parts in the system were established, and some indexes to evaluate system performance were given. Next, an indoor experiment was set up and tested. Based on the experimental results, this paper analyzed the effects of seawater spraying temperature, spraying quantity and the air volume flow rate on freshwater production rate and the gain output ratio (GOR). Finally, the economic analysis and freshwater yield per unit volume of this system were discussed. The results show that when T-s1 = 83 degrees C, m(s1) = 1.1 t/h and m(c1) = 0.94 t/h, the water yields of the HDH system with 560 m(2) total heat transfer area are 47 kg/h and 63 kg/h respectively under V-a = 0 m(3)/h and V-a = 300 m(3)/h. Compared with conventional systems, the current system has higher water yield per unit volume (34.1 kg/(m(3).h)) and lower pure water yield cost (3.86 $/ton) when the investment cost of the whole solar desalination device with 42 m(2) solar collectors is about $ 6563.