TC11 titanium alloy manufacture by Selective laser melting (SLM) technology has excellent specific strength and broad application prospects in the aerospace field. By conducting quasi-static tensile and dynamic compressive mechanical experiments on SLM TC11 titanium alloy that built in horizontal and vertical direction, the mechanical behavior of SLM TC11 titanium alloy under series strain rate loads was investigated; Based on EBSD testing, the effects of grain boundary strengthening and dislocation strengthening mechanisms on the dynamic compressive strength of SLM TC11 titanium alloy were explored. The research results indicate that the grain boundaries α_GB in the horizontally deposited specimens tends to aggregate cracks then exhibit lower plasticity during quasi-static tension; SLM TC11 titanium alloy exhibits significant strain rate strengthening effect and strong macroscopic isotropy during dynamic compression, adiabatic temperature rise will cause thermal softening, which compete with strain hardening can leads to a "plateau" characteristic in the flow stress plastic stage; Through statistical analysis of grain size and geometrically necessary dislocation density of dynamic compression specimens, it was found that the dislocation strengthening mechanism is the main strengthening mechanism of SLM TC11 titanium alloy during dynamic compression. Taking into account the effects of strain hardening, strain rate strengthening, and thermal softening, a J-C modified constitutive equation with higher accuracy than the J-C constitutive equation is proposed, which can accurately describe the dynamic mechanical behavior of SLM TC11 titanium alloy.