The invention discloses a system for generating electricity by utilizing liquefied natural gas cold energy and for a large LNG receiving station. The system is characterized in that three groups of independent heat exchange channels are arranged in a main heat exchanger, the inlet end and the outlet end of a first heat exchange channel are respectively connected with a liquefied natural gas pipe and a natural gas pipe, the outlet end of a second heat exchange channel is connected with a mixed working medium buffer tank, the outlet end of the mixed working medium buffer tank is connected with amixed working medium booster pump, the outlet end of the mixed working medium booster pump is connected with the inlet end of a third heat exchange channel, the outlet end of the third heat exchangechannel is connected with a mixed working medium heater, the outlet end of the mixed working medium heater is connected with the inlet end of an expansion machine, the outlet end of the expansion machine is connected with the inlet end of the second heat exchange channel, and the expansion machine is connected with a generator. The LNG cold energy is converted into electric energy by adopting low-temperature Rankine cycle with mixed working mediums, so that the system adjustability and the working-condition-varying adaptability are good, and the energy comprehensive utilization efficiency of the large liquefied natural gas receiving station can be improved.