• Population balance equation (PBE) is combined with particle-dependent adsorption kinetics equations to simulate gas-solid adsorption process on adsorbent with particle-size distribution. • Simulation results show that the adsorption behavior is significantly affected by the particle-size distribution of the adsorbent. • Approximation of particle-size distribution to volume-average size may lead to large underestimation of adsorption periods. The particle-size distribution of adsorbents usually plays an important role on the adsorption performance. In this study, population balance equation (PBE) is utilized in the simulation of an adsorption process to model the time-dependent adsorption amount distribution on adsorbent particles of a certain size distribution. Different adsorption kinetics model can be used to build the adsorption rate function in PBE according to specific adsorption processes. Two adsorption processes, including formaldehyde on activated carbon and CO 2 /N 2 /CH 4 mixture on 4A zeolite are simulated as case studies, and the effect of particle-size distribution of adsorbent is analyzed. The simulation results proved that the influence of particle-size distribution is significant. The proposed model can help consider the influence of particle-size distribution of adsorbents on adsorption processes to improve the prediction accuracy of the performance of adsorbents.