The Lanzhou urban reach of the Yellow River is subject to the comprehensive regulation of Liujiaxia Hydropower Station and Xiaoxia Hydropower Station，and the hydrological conditions of the reach are complex.To reasonably determine the design navigable water level，according to the hydrological characteristics of the river section and the relationship between the water level-flow of Lanzhou Station，the design flow is determined based on the comprehensive duration method，the assurance rate frequency method and the graphical fitting method.The Manning formula is used to determine the corresponding design water level at the end of the reach in combination with the hub dispatching operation mode.A one-dimensional mathematical model is built to study the design navigable water level of the reach.The design navigable water level of Lanzhou urban reach of the Yellow River is obtained.The results show that under the design maximum navigable flow，the engineering reach is in a natural state，and the design maximum navigable water level along the way can be calculated according to the combination of the 3 a return period flow and the tailgate water level calculated by the Manning formula method.Under the designed minimum navigable flow rate，the engineering reach is affected by the backwater of Xiaoxia Hydropower Station.Therefore，it is advisable to calculate the designed minimum navigable water level along the route based on a combination of 90% guaranteed flow rate and the water level in front of the Xiaoxia Hydropower Station dam.