Abstract: Nuclear power software needs to give the uncertainty of calculation results, thus it can effectively evaluate the safety of nuclear power. Nuclear data are important sources of uncertainty in core calculation, and the sensitivity analysis is an important step for the uncertainty analysis of core parameter. The sensitivity analysis of nuclear data is carried out on the critical calculation in Qinshan Ⅱ core. Firstly, Monte Carlo procedures are used for the establishment of Qinshan Ⅱs first cycle model, then the sensitivity coefficient of nuclear data is calculated with Iterated Fission Probability method(IFP) based on continuous energy cross section library CENACE V1.0 developed by Chinese nuclear data center. By the analysis of the sensitivity coefficient with different temperature and different burnup, the important nuclear data to be concerned in the uncertainty analysis of nuclear power software would be found.