In present work,the influence of three different microstructures on the mechanical properties and the fractures of the martensite type α-β titanium alloy,Ti-6.5Al-3.5Mo-2Zr-0.3Si,was investigated.These three types of mi-crostructures are the equiaxed structure with the volume fraction of equiaxed α about 50%;the mixed structure,consisting of the nearly equiaxed α and the distorted acicular tmorphology;and the lamellar structure which consists of Widmanstatten and grain boundary α It was found that the tensile,impact, high cycle fatigue and the room temperature tensile properties after prolonged exposure at 500℃ of the equiaxed structure are superior to those of the mi-xed and lamellar structures.The highest stress-rupture and creep strength were obtained in the mixed structure which appeared to havea better combi-nation of the properties than the others.The scanning electron fractographs showed that the dimple patterns were observed in the materials with equiaxed and mixed structures.The fractures of the material with the lamellar struc-ture were characterized as the intergranular fracture with the mechanism of microvoid coalescence.