Method for liquifying natural gas

A method for liquefying natural gas, in which a flow of pressurized natural gas is brought into heat exchange with two coolants flowing in closed circuits which are at least partly compressed, liquefied and expanded, the coolant in the first circuit being used to pre-cool the natural gas and the coolant in the second circuit while the coolant in the second circuit is used to liquefy the pre-cooled natural gas;

• the coolants in said first and second circuits comprising multiple components, after pre-cooling the natural gas down to approximately -50.degree. C., the natural gas is divided into major and minor streams, said major stream being liquefied by heat exchange with the coolant in the second circuit, while said minor stream being liquefied by heat exchange with the flash-gas formed when the liquefied natural gas is expanded and the liquid fraction separated, the flash-gas after heat exchange with said minor stream is compressed and is at least partly liquefied in heat exchange with the coolant in said first and second circuits, and is subsequently expanded and the liquid fraction separated.