The invention relates to a heat pump based all-weather sea water desalination system. The heat pump based all-weather sea water desalination system comprises a compressor, an evaporative condenser, a finned evaporator, a shall-and-coil evaporator, an electronic expansion valve, a flash intercooler, a turbocharger and a negative-pressure fan. If the temperature is relatively high in summer, and the temperature of the sea water is lower than the local temperature, the finned evaporator is used as an air source heat pump to heat to prepare the fresh water; if the temperature is relatively low in winter, and the temperature of the sea water is higher than the local temperature, the shell-and-coil evaporator is used as the sea water source heat pump to heat and manufacture the fresh water, and the boiling point of the sea water is reduced by utilizing the negative-pressure fan; the turbocharger is used for realizing one-stage compression of a refrigerant, and the compressor is used for realizing the two-stage compression of the refrigerator, so that the air suction volume of the compressor is increased; the flash condenser is utilized to raise the degree of the supercooling of the refrigerator in the major cycle, thus the benefit is provided for increasing the quality and the flow rate of the refrigerator in the major cycle, and as a result, the heating capacity is improved. By adopting the sea water desalination system, fresh water can be supplied for 24 hours a day at all seasons.