The main channel of the Yangtze River is characterized by numerous shoals,making the maintenance and dredging of the waterway a year-round task with numerous locations and points,posing great difficulties.To address the challenge of determining the appropriate timing for maintenance and dredging of the main channel of the Yangtze River,a study is conducted on the calculation method for the timing of maintenance and dredging in pebble (sand-pebble) river reaches of the main channel of the Yangtze River.By adopting methods such as theoretical analysis,experience summarization and field investigation,this study defines the dredging timing of the main channel of the Yangtze River,clarifies the key influencing factors of maintenance dredging timing for the pebble (sand-pebble) reaches,and establishes the principle of “precision-smoothness-unimpededness” for determining the dredging timing of channel maintenance.Furthermore,based on the laws of riverbed scouring and deposition,maintenance and dredging volume,post-floodwater level recession process,and construction efficiency of dredging vessels,a calculation formula for the theoretical optimal dredging timing in pebble (sand-pebble) river reaches of the main channel of the Yangtze River is established.The research results provide a calculation method for determining the dredging timing of the main channel of the Yangtze River,and can offer technical support for the design of channel maintenance and dredging.