The influence of Si content on mechanical properties of Ti-6Al-2Zr-1Mo-1V titanium alloy at room temperature and 500℃ was studied. The fracture morphologies and microstructures were analyzed by scanning electron microscope (SEM) and transition electronic microscope (TEM). The nucleation and growth of silicide were related to the mechanical properties. It was shown that the tensile strength and high-temperature enhance performance were improved when Si was added from 0.04wt% to 0.14wt% in the Ti-6Al-2Zr-1Mo-1V alloy; the ductility is almost unchanged; impact toughness and plane strain fracture toughness were decreased. The alternation tendency from ductility to brittle fracture can be found with the addition of Si, the radial region enlarged, and the area of fibrous region and shear lip minified. When the content of Si is less than 0.09wt%, the Si elements are dissolved in α and β phase and increase strength, solid solution strengthen mechanism is the main mechanism. On the other hand, the silicide precipices along phase boundary when the content of Si reaches 0.14%wt, which led a combined strengthening by solution and precipitation.