Potato as one of the most important sources of the human food is easily digested and has high quality protein. One of the most famous products of the potato is French fries. Frying is one the common methods for preparing the foodstuffs with specific characteristics. In traditional method, the product is soaked in the oil and heated at temperatures higher than the water boiling temperature under atmospheric pressure. Under these conditions, presence of oxygen along with the high temperature, cause structural changes in the surface and inside of the food material, losses in nutritional value, oil oxidation, enzymatic browning, as well as reduction in oil shelf life. Moreover, this method generates anti-nutritional material such as acrylamide and increases oil absorption within the material. Vacuum frying is a new technology that can improve the quality characteristics of the fried product. In this study, a laboratory food vacuum fryer system was designed and developed. The potato strips were placed in the frying basket inside an impermeable chamber under desired pressure provided by a vacuum pump. The frying chamber contained some oil that was heated to a desired temperature by using a control system. In order to prevent entering the water vapor produced during the frying process to the vacuum pump, a vapor trap system was used. At the end of the process, the basket containing the material was extracted from the oil. De-oiling mechanism extracted the surface oil through its rotational motion. After processing, the qualitative parameters including moisture loss, oil content, textural firmness for the crust and core of the slice, shrinkage, and total color difference were measured. According to the literature, the effect of pressure (55- 255 mmHg), oil temperature (95-155 °C), frying duration (3-15 min), and de-oiling duration during the cooling stage (0-100 s) on the measured parameters were studied. In order to optimize the conditions for the vacuum frying process, response surface methodology (RSM) was used and the models related to each parameter were determined and the accuracy of them were assessed. After determining the optimum conditions via the best-proposed model, to confirm the model performance the validation test was conducted. The pressure of 155.14 mmHg, oil temperature of 111.20 °C, duration frying of 6 min, and de-oiling duration of 64.84 s at a rotational speed of 300 rpm were determined as the optimum conditions for the vacuum frying process. Moreover, based on the previous studies, the traditional frying process was carried out at the oil temperature of 175 °C for 7 min, and de-oiling duration of 80 s at a rotational speed of 300 rpm. Then, the optimal vacuum and atmospheric frying processes were compared to each other. Results showed that during vacuum frying, moisture loss increases when the oil temperature, frying duration and vacuum pressure increased, and it was not significantly affected by the de-oiling duration. The oil content increased significantly with the oil temperature, frying duration and vacuum pressure. Increasing the de-oiling duration prevented from further surface oil absorption into the product. The firmness on the crust and core, and shrinkage increased with an increase in the oil temperature and frying duration. The oil temperature and frying duration had a significant influence on total color difference. Moreover, processing at lower temperatures and durations led to less color changes. Finally, the sample fried under the optimum vacuum conditions had significantly less discoloration, moisture loss, and oil content, but more shrinkage and textural firmness at the core in comparison with that fried under atmospheric conditions. Keyword: French fries, Modeling, Optimization, Response Surface Methodology (RSM), Vacuum frying.