Barley (Hordeum vulgare L. ) is an ancient and important cereal grain crop. Barley as an important food grain is mainly used in beverage industry for human consumption as well as used to feed directly to livestock for energy provision for production animals to produce milk and meat. As a grain, barley can not be consumed by livestock without being mechanically processed. Barley processing consists of making physical deformation in order to facilitate starch decomposition and break up by rumen digestive enzymes. Steam rolling is a physical wet processing method which requires heavy investment on steam equipment. To replace steam rolling with a less expensive method, soaking and heating process in a moisture-heat treatment system (MHTS) was performed. Rehydration process can take long time and does not guarantee a homogeneous distribution of water, the achievement of larger rehydration temperature has been proposed. The study of the rehydration kinetics of products is useful for process optimization; it is also of interest to know how the kinetics will be affected by processing variables and how the soaking time, under given conditions, can be predicted. Various barley seeds (Fajr, MB-863 and Reyhan03) grown in Isfahan Province in Iran, were used for the experiment in this study. Experiments were conducted in distilled water at 10 ْC, 20 ?C, 45?C for each type of barley at different duration. A Moisture-Heat Treatment System (MHTS) for barley flake processing was designed and fabricated in order to determine parameters on quality and quantity of processed barley. Factors in the experiment design included moisture (20, 25 and 30%), heat (60,70 and 80 ?C) and holding time (4,6 and 8 hour) with three replications. Processing index (PI) and particle size analysis was performed using a sieve shaker based on ASAE standards S424.1 after experiments were done passing samples through the processing rollers. The mean values for comparisons of different experimental treatments were examined through the LSD test at the probability level of . The results from this study showed that rehydration curves were greatly affected by the water temperature. Increase in the water temperature caused a decrease in the rehydration time. The effective moisture diffusivity values were calculated using Crank’s solution of second Fick’s equation for infinite plane sheet and were obtained between 4.4×10 -11 and 6.7×10 -11 m 2 s -1 for Reyhan03 cultivar, 4.4×10 -11 and 6.5×10 -11 m 2 s -1 for Fajr cultivar, and 4.0×10 -11 and 6.2×10 -11 m 2 s -1 for MB-863 cultivar. Empirical modeling of rehydration data was done by fitting to 10 commonly models used for rehydration processes. The performance of these models was assessed by statistical procedure. According to the maximum coefficient of determination (R 2 ) and minimum value of root mean square of error (RMSE) between the observed and predicted moisture ratios, the Verma model showed the best close prediction to the observed data. The theoretical modeling of rehydration data was done using numerical (implicit) solution of second Fick’s equation. The predicting model based on numerical solution of second Fick’s equation showed a good correlation with the experimental data. The result of comparison means showed that the experimental treatment of 30% moisture, 80?C heat and 8 hour holding time had the highest processing index (PI) and lowest rate of particles. Also, comparison means of chemical analysis indicated that this experimental treatment had the lowest neutral detergent fiber (NDF) and acid detergent fiber (ADF) amounts. Key words : barley, processing index, modeling, chemical analysis