Abstract: As the problem of inadequate waterway dimension in the upper Yangtze River is becoming increasingly prominent, it is important to evaluate the maximum dimension for waterway construction and planning. In this paper, the hydrological and topographic data measured in the Yibin-Chongqing reach are used to improve the river hydraulic geometry relation and water depth correction coefficient of the traditional stable waterway depth method. Based on the measured water levels of three characteristic flow discharges of 2230 m³/s, 12100 m³/s and 20291 m³/s, the relationship between the river hydraulic geometry parameters and flow discharge is obtained, and the measured data of Zhutuo station indicate that the relationship is reliable in the dry period. In addition, by introducing the cross-sectional shape coefficient, the relationship between the water depth correction coefficient and the design waterway width is established. The maximum waterway dimension of the Yibin-Chongqing section is calculated using the improved stable waterway depth method, and the results show that the waterway dimension of the Yibin-Chongqing reach can meet the standards for class-Ⅱ waterway 3.5 m×100 m and for class-Ⅰ waterway 4.5 m×150 m. The flow discharge increase of 400 m³/s for Xiangjiaba, compared with the designed value, can increase the waterway depth by about 0.39 m. This paper proposes an improved stable waterway depth method, which simplifies the calculation process of the maximum waterway dimension. It can provide support for the subsequent waterway construction and planning of the Yibin-Chongqing reach.