The invention discloses a method for improving ship rank of a tidal bank-line wharf and a semi-submerged harbor pool. The method is that: an openable and closable harbor pool similar to a ship lock is designed and constructed at the front edge of the tidal bank-line wharf and is combined with the wharf; after a cargo ship drives into a berth in the harbor pool through a gate of the harbor pool at high tide level, the ship lock is closed, the wharf begins to work; during the ebb-tide, the water level of the harbor pool is decreased to the designed water level of the harbor pool through a water overflow and discharge channel, then a harbor pool water supply system remains the water depth of the harbor pool; when the loading or unloading of the cargo ship is finished, the gate of the harbor pool is opened when the high tide level appears to ensure that the cargo ship drives away the operation harbor pool; the method of the invention adopts a semi-submerged harbor pool which consists of an enclosed pool wall, a harbor pool gate for ship in/out, a water overflow and discharge channel of the harbor pool, a harbor pool water supply system and a harbor pool operation control system; at least one pool wall is the front edge of the wharf, and at least one side is the gate of the harbor pool. The invention has the advantages of: simple and reliable method, small investment and quick effect, can effectively take advantage of the prior tidal wharf to retrofit or construct, can effectively improve the ship rank of the tidal bank-line wharf, has high resource utilization rate and so on.