Zr alloys are widely used in pressurized-water reactors as fuel cladding materials due to their low neutron absorption cross section and excellent radiation resistance. Aside from the aforementioned properties, Zr alloys have high strength, relative low density and many other excellent physical and chemical properties that make them promising structural materials used in the aerospace environment. Zr-45Ti-5Al-3V alloy is a high strength zirconium alloy which is newly developed for use in aerospace environment. The temperature in space environment can change from -100 ℃ to more than 100 ℃, so it is necessary to study the mechanical behavior of Zr-45Ti-5Al-3V alloy under different temperatures. In this work, mechanical properties of Zr-45Ti-5Al-3V alloy under different temperatures (-100, 25, 100 and 200 ℃) and strain rates (10^-4, 10^-3 and 10^-2 s^-1) were investigated. The microstructure of the Zr-45Ti-5Al-3V alloy is characterized by SEM and XRD. It is shown that the alloy is comprised of two phases: a lath-like a phase with hcp structure is distributed uniformly in the matrix comprised of a b phase with bcc structure. Quasi-static mechanical properties of Zr-45Ti-5Al-3V alloy were studied in temperature range of -100~200 ℃ under various strain rates (10^-4, 10^-3 and 10^-2 s^-1) using the Instron 5528 electric universal material testing machine. The results showed that the alloy possessed yield strength of more than 1355 MPa at room temperature and higher fracture strength in tensile test, but the elongation was small. With increasing temperature, the yield strength and the fracture strength of the alloy decreased, while the amount of plastic deformation increased. Under the condition of compression test, the yield strength also decreased with temperature increasing, while the plasticity and fracture strength reached maximum at room temperature. The influence of strain rate on the mechanical properties of the alloy was not significant under both tensile and compression tests.