The mechanism of negative linear thermal expansion (NLTE) of Ti-34Nb (wt.%) alloy after 90% cold rolling is investigated by X-ray diffraction, thermal expansion and transmission electron microscopy. From the results, it is observed that 90% cold-rolled Ti-34Nb alloy is composed of beta and alpha '' (Martensite) phases with the existence of < 110 > (beta) and < 010 > (alpha '') textures along rolling direction (RD). The cyclic thermal expansion, XRD and TEM studies show that when the thermal cycle temperature is at 100 degrees C, the RD of 90% cold-rolled Ti-34Nb alloy performs a reversible NLTE, which gradually weakens when thermal cycle temperature is at 300 degrees C, attributing to the gradual decomposition of alpha ''-phase. When thermal cycle temperature rises to 380 degrees C, the reversible NLTE disappears and turns into positive linear thermal expansion, meanwhile, alpha ''-phase decomposes completely. Based on the formation of beta and alpha '' textures by cold rolling and alpha ''<-> beta thermo-reversible transformation mechanism, the NLTE mechanism of 90% cold-rolled Ti-34Nb alloy is successfully explained. Moreover, according to the present results, a novel strategy is proposed to tailoring the negative coefficient of linear thermal expansion by changing alpha '' content, which improves the application potential of Ti alloys.