Abstract: In this paper, an integrated neutronics/thermal-hydraulic model for the reactor of Qinshan Phase Ⅱ NPP project was developed, using the RELAP5-HD as core coupled computational code. Based on the coupled model, the steady state calculation and the rod drop transient simulation were performed. The results show that the values obtained from RELAP5-HD calculation agree well with the available measured data, and the calculated accident curves can predict all major parameters trends of the transient with good accuracy. Both steady state and transient calculation results are in accordance with the theoretical analysis from the feedback aspect of coupled reactor neutronics/thermal-hydraulics, this demonstrates that a successful coupled model of Qinshan Phase Ⅱ NPP core has been developed, and the established model provides a good foundation for further simulation analysis of the nuclear power plant system.