The quasi-static and dynamic reload compression tests were conducted to explore the changes in mechanical properties of Ti6321 alloy bimodal structure after preshock. The optical microscopy (OM) and transmission electron microscopy (TEM) were used to observe and analyze the microstructures. The results show that the static and dynamic yield strength and average flow stress of Ti6321 alloy after pre-shock are higher than those of the original sample, but the fracture strain and impact absorption energy are significantly reduced, and the preshock sample is more likely to appear an adiabatic shear failure after SHPB loading. TEM results showed that twins were formed inside the sample after the preshock of the light gas gun, which caused the Ti6321 titanium alloy to exhibit a shock wave strengthening effect.