An amendatory Langmuir adsorption model is established based on an experiment using water vapor mixed in hydrogen and adsorbed onto a 5A molecular sieve film. The model is applied to simulate the computation of the desorbing process of the adsorption bed. The simulation curves of adsorption quantity, as well as the temperature vs. time of adsorption bed in the axial direction, are obtained. The thermal images of the adsorption bed are captured using an infrared camera to prove the result of simulation. The results of the simulation and the experiment are in agreement. The research shows that the desorbed water vapor mixed in the regenerating gas would re-condensate on the surface of the molecular sieve because of decreasing temperature and ascending humidity. The re-condensation of water vapor is concentrated on the middle of the adsorption bed. The failure of adsorbent is primarily attributed to the re-condensated water. Crown Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.