Abstract: Precursory cooling heat transfer has a key effect on quench front progressing velocity which is a symbol of core cooling efficiency during reflood phase. Therefore, the study on precursory cooling heat transfer characteristics is important. In the paper, the influences of initial wall temperature, inlet coolant temperature as well as inlet mass flow flux on precursory cooling heat transfer coefficients were investigated based on results of numerical method solving two-dimensional conduction equations and measured data from bottom reflood experiments in an annular channel. It is shown that precursory cooling heat transfer coefficients are independent on initial wall temperature, increase with the inlet mass flow flux, and decrease with the increase of distance from quench front. A heat transfer correlation of precursory cooling is obtained.