Abstract: At present, the most widely used air conditioner is vapor compression cooling systems driven by electrical power.The dehumidification method of vapor compression cooling systems is often to cool the air below its dew point, and so the approach consumes much electrical energy, particularly when the air should be reheated after the dehumidification process.Besides the traditional dehumidification method(cooling the air below its dew point), the air may also be dehumidified by liquid desiccant and the liquid may be regenerated by solar energy.As a result, solar energy driven liquid desiccant cooling systems have emerged as a potential alternative to conventional vapor compression systems for cooling and air conditioning.Two important parts of the solar liquid desiccant air conditioning system are the regenerator in which the weak solution is concentrated, and the solar collector in which solar radiation is transformed into heat energy.The 2 components may achieve their own functions respectively.The weak desiccant solution flows into the solar collector and absorbs the solar thermal energy, leading to the increase in its temperature, and then the heated weak desiccant solution flows into the regenerator and contacts with the passing air stream.In the regenerator, moisture is evaporated from the hot weak solution and then removed by the passing air, and as a result the weak solution is concentrated.On the other hand, solar collector/regenerators(C/Rs) are designed to achieve the dual functions of solar collector and solution regenerator for high regeneration efficiency.In order to increase the efficiency of solar solution C/R, a method of solar air pretreatment solution grading C/R is put forward in this paper.The solar air pretreatment solution grading C/R is chiefly made up of the first grade solar C/R, the second grade solar C/R and the packed bed dehumidifier.The first grade solar C/R adopts directly surrounding air for regenerating solution with low concentration that is used to dehumidify the regeneration air for regenerating solution with high concentration in the second grade solar C/R.Such design aims to increase regeneration efficiency of strong solution in the second grade solar C/R.A mathematical model on solar air pretreatment solution grading C/R is built by defining quality factor of evaporation rate of water vapor that is used to show difference of regeneration performance of different concentration solutions under other same parameters.In that model, effective solution proportion and effective storage capacity are defined to describe the performance of solar air pretreatment solution grading C/R.The simulation results show when the efficiency of heat exchange used for solution pre dehumidification is equal to 0.69, the effective storage capacity reaches the maximum.Moreover, the effective storage capacity increases with the increasing of the product of specific surface area and tower length.There are critical values for relative humidity of surrounding air and solar radiation intensity that are used for judging if the new solution regeneration method is superior to direct solar solution C/R.Simulation results show the critical values for relative humidity and solar radiation intensity are 60% and 780 W/m2 respectively under given simulation conditions in the paper.When the relative humidity of surrounding air is greater and the solar radiation intensity is weaker than its own critical value, solar air pretreatment solution grading C/R has greater superiority compared with traditional solar C/R.Finally, it is concluded that the proposed solar air pretreatment solution grading C/R performs satisfactorily for regenerating the solution with high concentration under the climates of high humidity and low solar radiation in southern China.