The effects of pulse current electrolysis conditions on the composition and the microstructure of Ag-Sn alloy were studied by using a pyrophosphate bath. Both cathode current efficiency and throwing power of alloy deposits formed under pulse plating conditions, decreased with increasing mean current density, and lower than those under D.C. electrolysis condition. Tin content of Ag-Sn alloy decreased noticebly with in-creasing the mean current density, while it increased with the increase of On-time from 1 to 10 ms. The pre-ferred orientation of Ag-Sn alloy changed with increasing cathode overpotential in the sequence of (100)longrightarrow(100)+(111)longrightarrow(111) at $20^{circ}C$ and (110)longrightarrow(111)longrightarrow(111)+(100) at $30^{circ}C$. The effective crystal grain size of the alloy was decreased by decreasing temperature from $30^{circ}C$ to $20^{circ}C$ and the surface structure of them was related to the preferred orientation.