One of the important parameters that affect the performance of solar collector is the ambient air temperature around the collector. Increasing ambient air temperature around the collector reduces the losses from the collector, which enhance collector efficiency. In the present work, theoretical investigation on solar collector under greep house effect is performed. The floor of transparent-wall enclosure is covered with a black pebbles bed as heat storage. From the theoretical model, the temperatures variation of air in enclosure, pebbles bed and collector during the day time for different values of enclosure transmissivity, bed thickness and enclosure volume, were evaluated. Also, the results for the collector performance in transparent wall enclosure and that for the collector in the open-air condition are compared. From the theoretical model, it is observed that the air temperature rise in the green house reached 20 C above ambient temperature. A corresponding enhancement of useful heat gain of about 12-18 % for the collector in transparent enclosure can be reached. The system continued functioning several hours after the sunset due to the energy storage in the system.