Tomato is used as raw or cooked material in salads, sauces, soups, and all kinds of foods. Most vegetables including tomato that are rich in vitamins, minerals, fat and carbohydrates, are cultivated seasonally. Due to excessive production of tomato, physical, microbial, and chemical effects in the absence of appropriate conservation methods will cause this seasonal product to be deteriorated in a considerable amount. One of the oldest and most extensive processes used to protect food against corruption is the drying process. This process increases the shelf life of the product by reducing microbial and enzymatic activities and the rate of chemical interactions. Moreover, via reducing the weight and volume of the product, it makes its packaging, traort, and storage easier. The most common method for drying fruits and vegetables is drying by hot air. Through this method, the material is exposed to a continuous flow of hot air that evaporates its water. Low energy efficiency and extended drying time during falling rate period are known as disadvantages of drying with hot air. One of the ways to overcome this problem is application of ultrasonic waves. Using ultrasonic waves as a supplement to the common hot air drying method increases the diffusion coefficient of moisture, and hence reduces the drying time. In this study, the effect of ultrasonic waves as a pretreatment in combination with hot air method on moisture loss kinetics, shrinkage color, water rehydration capacity, and nutritional value parameters of the tomato slices was investigated. The experimental tomato samples (Honey variety) were harvested from a greenhouse in Zarrin Shahr (Isfahan). The ultrasonic waves were indirectly applied to the whole samples by an ultrasonic bath at a constant power of 140 W and a frequency of 35 kHz at durations of 0 (no sonication), 15, 30, and 45 min. Then, the samples were sliced (in 4 mm thickness) and dried at air temperatures of 50, 60, and 70 °C, and air velocities of 1 and 1.5 m s -1 . The results indicated that the drying time decreased with increasing air temperature, air velocity, and duration of sonication. According to the drying curves, the falling drying rate period was completely observed from the beginning to the end. Variations in shrinkage percentage of the samples showed that the shrinkage increased with time and the highest shrinkage was related to the temperature of 70 °C. Interaction effect of ultrasound pretreatment and air velocity on water rehydration capacity was significant, and the highest capacity was related to the samples dried at air velocity of 1 m s -1 , and pretreated for 30 min. The total color difference of the dried samples increased with duration of ultrasonic waves. Preventing effect (antioxidant activity) analysis of the dried slices showed that the effect of temperature and ultrasonic pretreatment, as well as their interaction effect on this nutritional value index were significant. In addition, it was revealed that with increasing the duration of ultrasonic pretreatment, the amount of vitamin C decreased significantly. Moreover, the vitamin C decreased significantly with increasing temperature and increasing air velocity. Analysis of lycopene content of the dried tomato showed that its value increased with ultrasonic application and increasing drying air temperature. Keywords : Antioxidant activity, Hot air drying, Ultrasonic waves, Lycopene, Total color difference.