The phase diagram of gadolinium-tin system has been completed by X-ray method in conjunction with differential thermal analysis. Three new intermetallic compounds: Gd3Sn,Gd8Sn7 and Gd3Sn4, were observed.In this system, there exist eight intermetallic compounds:Gd3Sn,Gd5Sn3,Gd5Sn4,Gd8Sn7,Gd11Sn10,Gd3Sn4,GdSn2 and GdSn3. The intermetallic compounds Gd3Sn and Gd5Sn3 melt congruently at 1173℃ and 1243℃, and the intermetallic compounds Gd5Sn4, Gd8Sn7, Gd11Sn10, Gd3Sn4, GdSn2 and GdSn3 are foymed by Six peritectic reactions at 1179℃,, 1114℃, 1095℃, 995℃,941℃, and 905℃, respectively. Three eutectic reactions occur at 15at% Sn and 1103℃, 32at% Sn and 1141℃, l00at% Sn and 232℃ Neither Gd in Sn nor Sn in Gd Shows any detectable solid solubility.