In order to discuss the characteristics of aeration and hydrodynamic pressure of discontinuous outer convex step in spillway steep slope section，the hydraulic model test of aeration and hydrodynamic pressure of the steps in steep slope section with a gradient of 1∶3 is carried out. The study results show that, first，affected by the body of outer convex step, the length of non-aerationzone of the steep slope is shorter than that of conventional continuous internal concave step , the water air concentration at the steep slope wall is higher and increases along the slope in the downstream of water surface aeration initial section, and the air concentration increases with the increase of the step height and decreases with the increase of the unit-width discharge，the anti-cavitation properties of steep slope wall are obviously increased.Secondly，the hydrodynamic pressure intensity of the step steep slope wall increases as the step height and unit-width dischar increase and in the experimental conditions of the step height a≤0.6 m and the unit-width discharge q≤30 m3/(s·m)，the pressure value at the step steep slope wall is within limit of 45% of the velocity head of the corresponding section in the downstream of water surface aeration initial section.