In the paper, it uses the test-bed of the solar liquid desiccant air conditioning system to do the experimental research about the thermal performance of the solution in solar collector, and adopts LiCl solution as the work medium and U-tubular all-glass evacuated tube as solar collector. Adopt the heat collection efficiency and the solution temperature difference between inlet and outlet to describe the thermal performance of the solar collector. From the experimental data, it analyzes the influence of the various parameters, such as the solution volume flow, the inlet solution temperature, the solution concentration, the ambient temperatures and the solar radiation, on the heat collection efficiency and the solution temperature difference between inlet and outlet. The result shows that: the heat collection efficiency increases with the solution volume flow, the ambient temperatures and the solar radiation, but it decreases with the inlet solution temperature and the solution concentration. The solution temperature difference between inlet and outlet increases with the ambient temperatures and the solar radiation, but it decreases with the solution volume flow and the inlet solution temperature, and it first decreases and then increases with the solution concentration, and the critical solution concentration is 36.5%.