For the problem of optimal shielding design of metal shielding enclosures in complex environments, multi-layer cylindrical metal enclosures is modeled and simulated by using simulation software. In the simulation, the shielding effectiveness of the multi-layer enclosures with different diameter-to-length ratios and alternating combinations of different materials is compared and analyzed. The results show that the multi-layer shielding enclosure with optimal shielding effectiveness is composed of stainless steel on the outer layer, silver on the middle layer and permalloy on the inner layer. And the larger the length-diameter ratio of multi-layer cylindrical metal enclosure, the better the shielding effect. The simulation study of electromagnetic shielding effectiveness of multi-layer cylindrical metal enclosures provides support for the study of multi-layer metal shielding enclosures in complex electromagnetic environments.