Rb₂Ni₃S₄ is a Kagome system belonging to the space group Fmmm (Orthorhombic). Here we performed density functional theory (DFT) calculation using the full potential local orbital code (FPLO) and identified ferromagnetic ground state with low magnetic moment. We consider Co doping by replacement of Ni on Rb₂Ni₃S₄ . Interestingly half metallic ferromagnetic behavior is observed with a total magnetic moment of 1.999 µ_B / unit cell. This indicates that the material is suitable spintronics device application in Kagome system. Moreover, due to the strong localization of electrons the flat band is observed near the vicinity of Fermi level which would be supportive in the study of possible super conducting nature of the material.