The main objective of the present work is to give the results of theoretical investigations of a desiccant packed bed. For this purpose, the finite difference scheme is proposed and investigated numerically by solving the equation describing mass diffusion in the desiccant bed. This results in a tridiagonal system, which is solved by using Thomas Algorithm. Also, the mass transfer of water vapor and the energy balance equations in both air stream and solid desiccant are solved using the fourth order Runge – Kutta method. The analysis is carried out for typical inlet conditions of 28oC dry bulb temperature and 66% humidity ratio for desiccant masses (5, 10 and 15 kg) and air mass flow rates (7.4 and 10.2 kg/min) during dehumidification operation mode. The reactivation of the desiccant at different regeneration temperatures and air flow rates as well as desiccant masses is also investigated. For the same layer thickness the water content in the desiccant increases by 65% when the desiccant mass increased from 5 to 10 kg while it's increased by 170% when the desiccant mass increased from 5 to 15 kg.