The composition and the microstructure of the Sn-Ni alloy electrodeposited in pyrophosphate bath were investigated according to the electrolysis conditions. The cathode current efficiency increased with the addition of $NH_4CI$ and glycine, while it decreased with the increase of current density. The Sn content of the alloy deposits increased with the increase of $NH_4CI$ in the bath. The alloys with 51~71wt.% Sn had the NiSn single phase structure. The preferred orientation of the single phase alloys changed from (110) to (110)+(101) with the increase of current density and cathode overpotential. The single phase alloys with 50~60wt.%Sn had the smooth surface structure with fine crystallite, while the multiphase alloys showed the surface structure with crystal size and cracks at high curret density.