At present, a standard for drainage volume control for subsea tunnels constructed using the mining method does not exist. Drainage volume is affected by various complex factors, which vary with construction advancement and hinder the precise design of the drainage system. A case study is conducted on the Pearl river estuary railway tunnel to address these problems, and a drainage volume control method combining standard selection, process control, and dynamic adjustment is proposed. The study guarantees precise design parameters of drainage systems based on actual and theoretical drainage data of some projects built globally. Then, the applicable conditions, operational effects, malfunction rate, and engineering demands of submerged pumps are analyzed. Based on the results, it is recommended to adopt singlestage submerged pumps with simple craft, stable performance, and mature technology. Through stability and reliability analyses, it is also revealed that when the pump head exceeds the lifting power limit of the singlestage submerged pumps, the multigrade lifting of the singlestage submerged pumps becomes superior to the singlegrade lifting of multistage submerged pumps.