In this research, thin layer solar drying of Cuminum cyminum grains was conducted by means of a solar cabinet dryer. This system was employed in two drying states (mixed and indirect) and four levels of drying air flow rates (f : passive and f, f, f: active). The average initial moisture content of the plant for all 1 234 drying tests were about 43% on dry basis and the drying was performed continuously, in each test, for a period of 90 min. Drying rate of different drying methods as well as thermal efficiency of solar collector were obtained. The effects of drying air flow rates and drying methods are highly significant on final moisture content of Cuminum cyminum. Natural convection solar drying was selected as the best drying air flow rate because the product has fewer moisture content in each drying time. However, mixed mode has less moisture content comparison with indirect type in the same time. Finally, natural convection solar drying air flow rate in mixed mode was selected as the best drying method for drying of Cuminum cyminum grains. In addition, thermal efficiency of flat plate solar collector was calculated in three levels of active drying air flow rates. It is showed the higher drying air flow rate is the higher thermal efficiency of solar collector.