Abstract: Under sub-critical and near critical pressures, the heat transfer characteristics of the steam-water two-phase flow in the inclined upward smooth tube with the diameter of φ 32×3mm and the inclined angle of α ＝ 20 were investigated experimentally. The tests were performed at p＝ 13～ 21.5MPa, G ＝ 600～ 1200kg/(m²· s) and q＝ 200～ 600kW/m²。The results show that the wall temperatures and the internal wall heat fluxes non-uniformly distribute along the circumference of the inclined upward tube, and that the non-uniform distribution can be decreased and even eliminated by increasing the mass velocity. At different working conditions, the influence laws of the pressures on the heat transfer are different. The correlation of the minimum heat transfer coefficient of the inclined tube has been provided and can be used as a reference in the design of engineering practices.