Pressure swing adsorption process is one of the newest methods of gas separation that is economically well positioned in the separation processes. In this project, the pressure swing adsorption process for separating oxygen from air is simulated for a two bed unit. This process involves four steps pressurization, adsorption, blowdown and purge. In pressurization step, compass air is inserted at the first bed of the bed while the final part of adsorption bed is closed and the pressure is increased as the highest amount that is considered and then the adsorption step for the end of the column is open and the feed is also inserted from the first part, then the part that has lower adsorption ability is stayed in gas phase and then is leaved from the end of the bed. After the adsorption step, the blowdown step is surveyed. Blowdown in the upstream feed, which is performed from the top to down. At this point in the bottom of the bed, the part is partially absorbed is removed from the platform and purge is performed at the end of the level. In this purge, the bed is washed and cleaned up from adsorption bed and thus the adsorbent is relived in the regeneration phase. Purge action of bed is performed by some part of main product. To simulate each of these steps, the governing equations involving ordinary differential equations and partial differential equations are solved using COMSOL software. The governing equations are identical for all four stages and the difference is in the initial and boundary conditions. A pilot plant with two bed is used for testing that equipped with switching solenoid valves of streaming, digital flow meter, barometer and gas analyzer. Time and duration of the opening and closing valve is capable to plan by a computer program connected to a programmable device and the measured data are recorded and stored. The results of the simulation were compared with the results of the test and have a good match. These results include changes in concentration, pressure and speed variations over the bed, as well as the effect of adsorption pressure, blowdown pressure, time of adsorption step, the duration of pressurization step and flow rate of product to product purity. The results show that by increasing adsorption pressure and reducing the blowdown pressure, given that the used adsorbent is zeolite LiLSX and adsorption properties of zeolites is that at high pressure is performed with adsorption action and low pressure is performed desorption operation causes to increase purity of the product. Moreover by increasing the time of pressurization step, the time of adsorption and decreasing flow rate of product the product purity are increased. Keywords : ressure swing adsorption process, zeolite, compact bed, products purity, concentration variations