Abstract: In the case of severe accident evaluation,supercritical water-cooled reactors will take advantage of the natural circulation driving forces to carry the core waste heat in the cycle.But there are many factors influencing the supercritical water heat transfer coefficient.Quantitative determination of the influence of each factor on the heat transfer coefficient has certain practical reference value for improving the design of supercritical water-cooled reactor.Based on the experimental data of supercritical water in natural circulation,seven factors are selected to analysis the HTC（heat transfer coefficient） using the grey relational model.The factors include heating power,diameter,system pressure,inlet temperature,outlet temperature,wall outlet temperature and system circulation flow rate and so on.Through the analysis,we can get that the resolution has important effects on the grey relational model result.Through the analysis of the grey correlation degree about heat transfer coefficient,it can provide theoretical basis for the prediction of heat transfer coefficient.