The paper mainly studied the strength variation and microstructure of the biomedical Ti-15Mo titanium alloy after the solution and aging treatments. And the hardness variation of the alloy in different aging conditions also was studied. Through analysis of the relationship of the alloy strengthening effect and microstructure, the alloy strengthening effect would be discussed due to the different transformation and microstructure, and reveals the Ti-15Mo titanium alloy strengthening process and its formation mechanism. The study on the mechanism of the alloy systematically, will be use for provide good theoretical basis for material evaluation and the application.