System-in-package (SiP) encloses multiple dies in a single package which is much sensitive to electromagnetic interference due to its intensive internal density and complicated internal structure. This paper presents computational analysis of shielding performance by modelling, simulation and optimization of a radio frequency integrated circuit (RFIC) in SiP using a self-developed virtual electromagnetic compatibility (VEMC) system. The system is designed and proved for computational electromagnetics needs in high performance computation and visualization. Multi-objective optimisation in package thickness, material conductivity, number and order of shielding derives an optimal shielding effectiveness for the discussed package.