In order to provide technical parameters for waterway regulation, wharf construction, flood control and lock design of the Minjiang River, in the absence of field data, numerical simulation, field observation and correlation analysis were used to calculate the lowest navigable water level in the downstream channel of Minjiang Shuikou Hydropower Station. Based on unstructured grid and finite volume method, a two-dimensional hydrodynamic numerical model was established from Shuikou Hydropower Station at the Minjiang River to the Mawei River, which was used to calculate the hourly water level at the downstream channel of the hydropower station. The hourly water level of the downstream channel was used to establish the correlation with the water level of Zhuqi, Wenshanli, Baiyantan and other long-term hydrological stations (base station). The cumulative frequency method is used to calculate the water level characteristic value of 90% of the cumulative frequency of the low tide as the design lowest navigable water level of the reference station. The calculation results show that the linear relationship of the hourly water level is well correlated between base stations and temporary stations with a correlation coefficient higher than 0.9, indicating a rational and reliable design lowest navigable water level.