Abstract: The incipient boiling wall superheat of sodium flowing in annulus was experimentally investigated. The annulus is the length of 800 mm, the inside diameter of 6 mm and the outside diameter of 10 mm. Experimental conditions are that the heat flux is 128-846 kW/m², the inlet subcooling is 63.1-287.8 ℃, the mass flow rate is 7.2-122.0 kg/h and the system pressure is 0.85-28.79 kPa. The experimental results indicate that the incipient boiling wall superheat increases with the heat flux and the inlet subcooling, and reduces with the increase of the mass flow rate and the system pressure. A semi-empirical correlation was gained from experimental results. The predicting results agree well with experimental data.