The Monte Carlo calculation method was used for the adsorption of mobile molybdenum oxide in ZSM-5 zeolite pores. Two models of mobile Mo species were designed and their adsorptions in ZSM-5 zeolite pores were investigated, respectively. The simulation calculation results suggest that the tetrahedral coordinated MoO2(OH)(2) should be the possible mobile Mo species in ZSM-5 zeolite pores. The maximum loading of MoO2(OH)(2) molecules per unit cell of ZSM-5 was determined as 5, and this sorbate prefers to locate at the intersections of the straight and zigzag channels of ZSM-5 zeolite. The average adsorption energy and isotherm energy per MoO2(OH)(2) molecule in ZSM-5 zeolite was -5.80 kcal/mol and 1.54 kcal/mol K, respectively, at 773 K. The interaction between MoO2(OH)(2) and ZSM-5 framework was dominated by the van der Waals energy.