Numerical simulation for hydrogen-recovery multibed PSA process was performed by orthogonal collocation method for the feed mixture gas of hydrogen, carbon dioxide, carbon monoxide, and methane in petrochemical plant. A fourbed and nine-step process using a layered-bed which was consecutively packed with two different adsorbents in one bed was employed to produce high-purity hydrogen. The packing raito of zeolite to activated carbon affected the purity and recovery of the product. The optimum length of zeolite layer and that of activated carbon layer were 60cm each. The optimum adsorption pressure and feed velocity could be determined to be 19 atm and 11.0 cm/s, respectively, for given packing ratio. The recovery and purity of the product were strongly affected by Difference-Pressure(DP) which was defined as the difference between the initial high pressure and the final low pressure at the cocurrent blowdown step which delivers purge gas to the low pressure bed. When the DP was larger than 1.3 atm, the purity did not change much and the recovery was continuously decreased with increasing DP. As DP increased, the pressure at the pressure-equalization cocurrent depressurization step was lowered and the pressure at the pressure-equalization countercurrent pressurization step following purge step was also lowered. Therefore, the amount of the high-pressure product to pressurize the low-pressure column increased.