Abstract To reduce pollutant emission of gasoline engine during cold start, ZSM-5 zeolite was selected as adsorbent and coated on cordierite carrier and encapsulated as a hydrocarbon (HC) catcher. The hydrocarbon catcher was connected to an engine bench and the cold start experiment was carried out on the engine bench. The low-speed section of World Light Vehicles Test Cycle (WLTC) was used as the real road cycle to study the cold start emission of gasoline engines. The real-time emissions of hydrocarbons before and after the hydrocarbon catcher were measured and compared. The following results were obtained: in the first 41 s, the adsorption efficiency could reach 78%. From 41 s to 108 s, most of the adsorbed hydrocarbons were desorbed. After 108 s, chemical adsorption played a leading role. The total adsorption efficiency was 26.2% in the whole cycle. Results showed that ZSM-5 was an excellent HC adsorbent for cold start of gasoline engine. Molecular simulation based on the Monte Carlo method was applied to help understand the adsorption behavior of propene on ZSM-5 zeolite. Results showed that the priority of propene adsorption sites was: channel intersection near the compensation cation > channel intersection > center of the channels > the outer ring of the channels.