An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.