In this study, first principles calculation results of the half-metallic ferromagnetic Heusler compound Co2MnSi are presented. All calculations are based on the spin-polarized generalized gradient approximation (σ-GGA) of the density functional theory and ultrasoft pseudopotentials with plane wave basis. Electronic structure of related compound in cubic L21 structure is investigated up to 95 GPa uniform hydrostatic pressure. The half-metal to metal transition was observed around ∼70 GPa together with downward shift of the conduction band minimum (CBM) and a linear increase of direct band gap of minority spins at Γ-point with increasing pressure. The electronic density of states of minority spins at Fermi level, which are mainly due to the cobalt atoms, become remarkable with increasing pressure resulting a sharp decrease in spin polarization ratio. It can be stated that the pressure affects minority spin states rather than that of majority spins and lead to a slight reconstruction of minority spin states which lie below the Fermi level. In particular, energy band gap of minority spin states in equilibrium structure is obviously not destroyed, but the Fermi level is shifted outside the gap.