The work aims to simulate and analyze the effect of the structure changes of substrate PE on the adsorption of ethylene by Monte-Carlo method and to show the adsorption process of ethylene by the new active packaging material PE/molecular sieve membrane from the microscopic angle, so as to reveal the mechanism of the microscopic absorption. Material Studio software was applied to build PE/molecular sieve polymer model with different polymerization degrees and different molecular chain quantities. The adsorption process of ethylene by PE/molecular sieve system was simulated by Monte-Carlo method and the adsorption isotherm was drawn to analyze the absorption effect. The results showed that the adsorption capacity of ethylene from PE/molecular sieve system decreased with the increase of polymerization degree, and increased with the increase of molecular chain quantities. Also, the adsorption capacity significantly fluctuated in a certain range after reaching the adsorption equilibrium. Different substrate structures have a great impact on the adsorption effect of active packaging material PE/molecular sieve membrane. Under the same conditions, PE/molecular sieve packaging system with low polymerization degrees and large molecular chain quantities is more beneficial to the adsorption of ethylene. Also, the adsorption equilibrium is a dynamic equilibrium where adsorption and desorption occur at the same time.