Abstract: Experimental investigation on the heat transfer and flow of supercritical pressure water flowing in the sub-channel of SCWR,which was simulated by a vertical triangular channel,was conducted at the pressures of 23~28 MPa,mass fluxes of 700~1300 kg/（m²·s） and heat fluxes on the inner wall surface of 200~800 kW/m².The corresponding diameter of the fuel rod is 8mm and the ratio of pitch to diameter is 1.4.The effects of heat flux,pressure and mass velocity on the heat transfer characteristics were analyzed.Experimental results showed that the wall temperature increases and the peak of heat transfer coefficient decreases with the increasing of the heat flux and pressure when other parameters remain unchanged.Improvement of mass velocity can enhance the heat transfer,which is characterized by the lower wall temperature and higher heat transfer coefficient.However the intensify effect of mass velocity on the heat transfer performance is not obvious when it reaches a certain level.The wall temperature varies dramatically with the increasing of the enthalpy and the peak heat transfer coefficient is much lower than that of the lower heat flux when the heat flux reaches 800 kW/m².And the enhanced heat transfer that usually appears in the large specific heat region is greatly weakened when the pressure rises up to 28 MPa.