Abstract: The Microstructure evolution during cold rolling with five processes of Ti-15-3 alloy and the microstructure and mechenical properties after rolling and aging treatment were investigated by using optical microscopy,transmission electron microscopy and X ray diffraction.The results show that 0.6 mm sheet could be obtained after rolling the sheet with thickness of 2.9 mm through three different cold rolling processes in unidirection.The grain size was refined to nanoscale with a minimum size of 19.1 nm.After 40%/pass-3 passes cold rolling and aging at 450℃ for 4 h,bidirectional nano-structure in the solution treated alloy was found which improved the ultimate strength of the alloy to 1 562 MPa,that was increased by 45% compared with the cold-rolled alloy.