Abstract: The effects of different finish cooling temperature and holding time on microstructure, precipitation behavior of Nb-Ti microalloyed steel were investigated by using Gleeble 3800 thermal mechanical simulator, transmission electron microscope(TEM) and nanoindentation instruments. The results showed that with the increase of the finish cooling temperature, the size of ferrite and the fraction of pearlite increase, and the fraction of bainite reduces, the Vickers microhardness increases first then decreases and reaches the maximum when the finish cooling temperature is 640°C. Rows of interphase precipitate and randomly dispersed precipitates can be found in ferrite matrix when the holding time is 0?s, and when the holding time is 100 s, the main precipitation is randomly dispersed precipitates. With the increase of the holding time, the nanoindentation is reduced 140 MPa.