The mechanical response of ? precipitations in a Ti-15Mo alloy during compression test is investigated by transmission election microscopy (TEM) observation. The interaction between the dislocation slips and ? precipitations was focused, by which some of the ? variants were absent, while others were detected, in deformation bands. Two mechanisms including the shear and the disordering mechanisms are proposed to uncover the underlying mechanisms of mechanical responses of ? precipitations. This understanding will provide new insight onto the strengthening strategy and alloy design of titanium.