Abstract: The behavior of second-phase particles in IF steels during annealing prcx:ess was investigated in detail. The results show that the size* shape and dispersion of second-phase particles forming before annealing, such as TiC, change differently in batch annealing (BA) in comparison with continuous annealing (CA), and two kinds of second-phase particles not existing before annealing here, FeTiP and (Ti, Mn)S, precipitate in BA but not in CA. It has been rarely reported so far that FeTiP precipitates and Mn exists in (Ti, Mn)S form in IF steels with low P (≤ 0.01%) and low Mn (<0.2%) during BA. In addition, the dispersion, the phase structure of the two phases were studied, and their potential contribution to the production of IF steels through BA is also discussed.