Adsorption behavior and microscopic structure of propane adsorbed in slit micropores are studied by using the grand canonical ensemble Monte Carlo (GCEMC) method, Non-polar propane molecule is modeled as a spherical LJ molecule and the 10-4-3 potential is used for the description of the interaction between propane and a slit pore in the GCEMC simulation, The adsorption, desorption, and capillary condensation have been simulated, The adsorption isotherms and local density profiles in slit pores have been obtained by the GCEMC simulation at T = 134.3 K, The microscopic structure of fluids confined in the slit pores is analyzed in detail, which indicates that the GCEMC method is a good tool to understand the microscopic mechanism of adsorption.