First-principles calculations were used to calculate the structural, electronic and half-metallic ferromagnetism of Mn2RuGe1-xSnx (x = 0, 0.25, 0.50, 0.75, 1) Heusler alloys. The Hg2CuTi-type structure is found to be energetic more than Cu2MnAl-type structure for both Mn2RuGe and Mn2RuSn compounds. The calculated lattice constants for Mn2RuGe and Mn2RuSn are 5.91 angstrom and 6.17 angstrom, respectively. The electronic band structures and density of states of Mn2RuGe show a half metallic character with total magnetic moments, 2 mu(B) per formula unit that are in good agreement with Slater-Pauling rule with indirect band gap, 0.31 eV along the direction Gamma -X. It is observed that the total magnetic moment per cell increases as Sn concentration increases in the Heusler alloys.