The invention discloses a novel four-purpose system capable of cooling, heating and providing hot water and fresh water by using a heat pump of seawater. The novel four-purpose system is characterized in that the system comprises a heat pump system, a fresh water preparation system and a hot water preparation system, wherein the heat pump system includes a compressor (1), a heating condenser (3), a first throttle valve (4), a refrigerating evaporator (5), a gas-liquid separator (7), a liquid reservoir (8), a refrigerant loop solenoid and a water side loop solenoid. The fresh water preparation system comprises a coil condenser (2), a first air channel (18), an inlet air pre-heating heat exchanger (9), a spraying room (10), a water baffle (16), an evaporator (6) for desalting, a second throttle valve (50), and a solenoid (19). The hot water preparation system includes a heat exchanger (11) for preparing hot water, a first air channel (15) and a solenoid (20). The system has the advantages of compact structure, multiple purposes, high-efficiency utilization of waste heat, lowered cost and reduced space.