Effects of different yttrium contents , such as 0, 0. 1%, 0. 3%, 0. 5%, 0. 7%, 1. 0%, on micro-structure and tensile strength at room temperature of Ti-47Al-xY alloy have been investigated systematically. The results show that with the increase of yttrium content, the columnar crystal in alloy is changed into equiaxed crystal with the yttrium content more than 0. 3%, and the grain size and lamellar space are decreased remarkably. With yttrium content more than 0. 1 % , when fine YA12 particle is uniformly distributed in the grain, some YA12 particles begin to segregate from the boundary in the alloy. Furthermore, the segregation from boundary becomes more and more serious with increasing in Y content. YAl2 phase is closed to form network with 1% Y content. Tensile testing indicates that the Ti-47A1 alloy with 0. 3% -0. 5% Y content possesses higher strength and plasticity. Size and distribution of YA12 phase in the alloy has the significant effects on properties of the alloys. As fined microstructure and fine YA12 phase in the grain is beneficial to improving the properties of the alloy, large YA12 phase enriched in boundary can greatly deteriorate the properties of TiAl alloy, especially Y content more than 0. 5%.