The pistachio nut ( Pistachia vera .) is one of the favourite tree nuts of the world and is widely cultivated in saline, dry and hot areas. Proper harvest and good processing are the major basis of having good quality. Drying of agricultural products has always been of great importance for the preservation of food by human beings. Cabinet drying are well-known food preservation techniques that reduce the moisture contents of agricultural product, and thereby prevents deterioration within a certain period of storage time. Drying influence physicochemical and quality characteristic of products, thus, modeling of drying kinetic is one tool for process control. Evaluation of drying kinetic as a function of drying conditions and determination of sorption isotherms and water diffusivity could help us in drying simulation for predicting the suitable drying conditions (air temperature, air velocity, relative humidity and drying time). In this reaserch, firstly, sorption isotherms of Pistachio nut (cv Ohadi) were measured in different tempretures (25, 40, 55 and 70°C) and then, 12 different models which are semi-theoretical and/or empirical were were fitted to the experimental data. The used comparison criteria to select the appropriate model were the coefficient of determination (R 2 ), the root mean square error (RMSE) and the reduced chi-square (? 2 ). According to the results, the GAB model for whole and pistachio kernel, and the Smith and Caurie models for husk of pistachio gave higher R 2 and lower RMSE and ? 2 values in compared to the other models. Secondly, the values of the water diffusion coefficient, the shrinkage, the colour and the rehydration ability of pistachio kernels during drying at the different temperatures were estimated. Effective water diffusivity values in different tempretures (50, 60, 70 and 80°C) ranged from 1.03 × 10 -10 to 3.73 × 10 -10 m 2 /s. Shrinkage and rehydration ability of food materials during air drying adversely affects the quality of the dried products. The experimental shrinkage data showed a linear behavior with moisture content, shrinkage increase with increase of drying time and decrease of moisture value. The experimental data didn't show the dominating effect of temperature on the shrinkage, the colour and the rehydration ability of pistachios during drying. Finally, a numerical model was developed to simulate the moisture transfer during of drying of a spherical pistachio kernel by finite difference method on MATLAB software. The predicted water loss content was validated by comparison with the experimental values (R 2 0.99). It can be concluded that this model describes well the mechanism of moisture diffusion during drying of the pistachio kernels. Key Words : Drying, Mass Transfer, Numerical Modeling, Pistachio, Sorption Isotherms.