In this study two simple mathematical models are proposed to describe the drying process of wet particles in a coaxial impinging stream dryer. The models represent the particles in two conditions, surface and internal moisture, which are solved numerically. The effect of various parameters including particle diameter, air velocity, and air temperature are investigated on the final moisture content of the product. In addition, drying intensity of the coaxial impinging stream dryer is compared with the other common dryers. This comparison leads to the conclusion of the high efficiency of impinging stream dryers at higher air velocity and smaller particles. Comparing the results of the models with available experimental data shows that the numerical predications are in good agreement with the experimental ones.