A phase diagram of the alloys of the Dy-Sn binary system has been investigated by means of X-ray diffraction method and differential thermal analysis. The intermetallic com- pounds DySn2,Dy5Sn3,Dy5Sn4 and Dy11Sn10 were detected, and the new intermetallic Compounds Dy2Sn,DySn,Dy8Sn9,Dy4Sn7 and DySn4 were observed.There are four eutectic reactions and six peritectic reactions in Dy-Sn system. Dy2Sn,DySn,Dy4Sn7 melt congruently at 1237℃, 1222℃ and 1154℃ respectively, and Dy5Sn3,Dy5Sn4,Dy11Sn10,Dy8Sn9,DySn2 and DySn4 decompose at peritectic reaction temperatures 1140℃, 1160℃, 1175℃, 1134℃, 738℃ and 442℃ respectively. There exists a Crystal melting transformation at 1182℃ in Dy-rich region.DySn4 does not show any detectable Solid solubility in Sn and Sn shows solid solubility up 5 wt% to in α-Dy and 7 wt% in β-Dy.