Abstract: In order to explore the influence of ship lock discharge on water level change and ship navigation in the Sanjiang lower approach channel of the Gezhouba Hydro-complex, the water level fluctuation characteristics in the approach channel were studied by prototype observation and statistical analysis. Based on the observation data at the early operation stage of the Gezhouba Hydro-complex and the flow pattern along the two sides of the approach channel, nine pairs of water meters were symmetrically arranged along the two sides of the approach channel, and the water levels in the channel under different discharge combinations of No. 2 and No. 3 locks were observed synchronously. The results showed that when the interval time between the two locks was 0 ~ 8 minute, the water potential energy was superimposed, while the water potential energy was offset after 8 minute. The minimum trough observed by the prototype observation was 0.75 m, and the interval time between the two locks should be greater than 8 minute in dry season. Within 14~38 minute after the lock discharge, the water level in the Sanjiang Station was lower than that of Miaozui Station, which had a negative impact on navigation, and traffic organization and channel observation should be strengthened.