Tomatoes is highly perishable and drying is one of the convenient methods of extending its shelf life and minimizing postharvest losses. Drying of tomatoes slices by normal microwave oven (home microwave oven) was investigated to determine the optimal drying conditions (either microwave powers or pretreatment) to produce a good quality product. So the effects of microwave powers and pretreatments on the drying time and quality of dried product in terms of moisture, TSS, polyphenol, lycopene, Ascorbic acid, carotenoids and rehydration ratio, were investigated. The experiments performed with three levels of microwave powers (750w , 1200w and 1500w) and four pretreatments ( control, 0.1% kHso3 , 1% CaCl2 and 1% citric acid ). The results indicated that, drying time was 44, 54 and 90 mn for 1500w , 1200w and 750w, respectively. Aso the results showed that, all studied microwave powers and pretreatments led to slight changes in moisture, TSS, acidity and rehydration ratio (for both 32C°, 50C° and 70C°). While lycopene, carotenoids, polyphenols and ascorbic acid contents obviously affected either by microwave powers and pretreatments. The balanced effect on rising lycopene,  carotenoids and polyphenols contents and in the same time on degradation of ascorbic acid was observed for microwave power of 1200w, while the most effective pretreatment on rising lycopene,  carotenoids and polyphenols contents and in the same time on degradation of ascorbic acid was CaCl2 treatment for each power separately.