Abstract: To improve the thermal performance of the unglazed solar air collector,a solar air collector using slit jet is designed,and its performance is analyzed experimentally and numerically. The simulation results of the internal flow and heat transfer characteristics of the collector show that the wall-attached slit jet formed by the circular holes and baffles can effectively cover the perforated absorber plate and thus improve the convective heat transfer between the air and the absorber plate. The optimal width of the slit is 3 mm when the diameter of the circular hole is 25 mm. The heat collection efficiency increases with the increase of baffle diameter because of the strong wall attachment effect. The experimental results show that the all-day thermal efficiency of the slit-jet solar air collector is stable and efficient. The all-day thermal efficiency of this solar air collector is up to 48% when the flow rate is 39 m~3/h,which is better than the traditional unglazed solar air collector.