The invention relates to a marine seawater source heat pump hot-water tank. The marine seawater source heat pump hot-water tank comprises a seawater source heat pump system. The seawater source heat pump system comprises a compressor, a condenser, a plate heat exchanger and a dry filter. A refrigerant water inlet and a refrigerant water outlet of the condenser are connected with circulating seawater. A refrigerant outlet of the condenser is connected with a refrigerant inlet of the compressor. A refrigerant outlet of the compressor is connected with a refrigerant inlet of the plate heat exchanger through an oil separator. A refrigerant outlet of the plate heat exchanger is connected with a refrigerant inlet of the condenser through the dry filter. Two thermal expansion valves in parallel connection are connected between the dry filter and the condenser in series. An energy control branch is connected between the output end of the compressor and the input end of the dry filter in series. An expansion valve and an electromagnetic valve are connected to the energy control branch in series. A pressure-bearing water tank and a circulating system are connected between a refrigerant waterinlet and a refrigerant water outlet of the plate heat exchanger. The input end of the pressure-bearing water tank is connected with a pressure water tank. The output end of the pressure-bearing water tank is connected with a water consumption device.