We have performed the volume optimization followed by the calculation of electronic structure and magnetic properties on Co₂MnSi and Co₂CrSi. The structure optimization was based on generalized gradient approximation (GGA) method. The calculation of electronic structure was based on full potential linear augmented plane wave (FP-LAPW) method and exchange correlation. Results of density of states (DOS) and band structures shows the half-metallicity of Co₂MnSi and Co₂CrSi with  an integer value of magnetic moments 5.031 µ_{B ­} and 4.006 µ_B respectively which follows the Slater-Pauling rule.