The effect of aging time on microstructure and mechanical properties of Ti-5Mo-5V-6Cr-3Al alloy tube prepared by cold rolled for high pressure gas cylinder was investigated in this paper. The results show that α phase size and phase content of cold rolling tube increased rapidly in 1 hours at 560℃ , and the tensile strength firstly increased and then decreased because which was affected by the size and content of α precipitates and dislocations and deformation twins, furthermore, plastic increased rapidly only owing to α phase size and phase content. Alpha precipitates grew slower and α phase content increased slower in 1- 4 hours, and the tensile strength firstly increased and then decreased because which was only affected by α phase size and phase content, meanwhile, plasticity continued to rise to the peak. Although α precipitates size and phase content most slowly increased in 4- 24 hours, but both of the tensile strength and plasticity decreased because of the coarsening α phase, in other words, over aging occurred.