Spall microstructure characteristics and failure mechanism of Ti-6Al-4V and Ti-47Nb titanium alloys were studied through plate impact experiments and “sample soft-capture” technology at the dynamic high-pressure loading, as well as careful microscopic analyses using optical microscopy and scanning electronic microscopy. The experiment indicates that Ti-6Al-4V alloys have stronger ability of spall resistance than Ti-47Nb alloys because of the high strength of Ti-6Al-4V alloys. The micro-voids in the spalled Ti-6Al-4V alloys almost nucleate at the α/β phase boundaries and propagate along the phase boundaries, and the micro-cracks of Ti-47Nb alloys are direct connected through micro-voids. Subsequently, adiabatic shear band formed between macroscopic voids or main cracks promote the spall fracture of samples. Ti-6Al-4V and Ti-47Nb alloys fracture with ductile characteristics.