Solar air collectors are important components for solar energy utilization in green houses. In this paper, experimental studies were carried out regarding to a solar air collector (SAC), for which the length of air channel is 1500 mm, the width is 500 mm, and a variable air channel gap ranges from 100 to 500 mm. In the experiment, the uniform heat flux along, the air channel is effected by three electric heating plates, which play a role as solar radiation. It is found that the temperature distribution of air and the induced natural air-flow rate are highly dependent on heat input, inclination angle, channel gap, etc. Experimental results indicate that the optimum inclination angle for the SAC is 45degrees, under which a maximum natural ventilation rate can be created. Also found is that there exists an appropriate channel length. about I in in this study, beyond which the obtained heat and the natural ventilation rate cannot be increased drastically. Higher the volume of air-flow rate through the SAC. lower the temperature difference between inlet and outlet, consequently, it should be balanced between the air temperature rise and a suitable mechanical air-flow rate in order to obtain maximum heat. Additionally, theoretical analysis based on heat balance equations is testified to agree well with experimental results. (C) 2004 Elsevier B.V. All rights reserved.