Compared with mountain tunnels, subsea tunnels face more serious waterproofing and drainage situations. Especially for long tunnels, keeping the tunnel dry and clean is a basic safety requirement. For the design of the waterproofing system of tunnels, the principle of "preferential water sealing, limiting drainage, adopting rigid and flexible system simultaneously, multiwaterproofing methods, adjusting waterproofing measures to local conditions and comprehensive treatment" is followed. Taking Jiaozhou Bay subsea tunnel as an example, the authors make primary study on the waterproofing and drainage measures, including advance pregrouting, leaking water treatment after excavation, waterproofing by means of waterproofing membranes and drainage measures. The engineering practice proves that the waterproofing and drainage measures taken are effective.