In this study, three grain-oriented silicon steels with different Nb contents were designed to investigate the effect of Nb on the behaviors of inhibitor solution and precipitation by Thermo-Calc software combined with TEM technology. The influence of Nb on precipitation rate of inhibitors in the silicon steels was also discussed. The results show that besides MnS and AlN, Nb(C,N) also exists in Nb-containing silicon steels, and with the increase of Nb content, the precipitation temperature and maximum mole fraction of Nb(C,N) increases significantly. Different Nb contents have no obvious effect on MnS. While the precipitation temperature of AlN decreases from 1190°C to 1140°C with Nb addition from 0.044wt% to 0.09wt%, but the maximum mole fraction of AlN does not change. According to the PTT (Precipitation-Time-Temperature) curve, Nb addition accelerates the precipitation process of second phase particles and shortens the incubation period. Combining the theoretical calculations with TEM analyses, it is known that proper Nb addition in the silicon steel can reduce the slab reheating temperature. Whereas, with excessive Nb addition, the inhibitors can not dissolve into the matrix totally at 1250°C, which will have a negative effect on the production of grain-oriented silicon steel.