The present invention relates to the control systems of the compression refrigerating machines, namely, to the methods of control of the natural gas liquefaction process to produce liquefied natural gas (LNG), and can be used for liquefaction and cooling of natural gas on the most major technological lines and LNG production plants, working on the mixed refrigerant (MR). The method of control of the natural gas liquefaction process on the mixed refrigerant-operating LNG production plant comprises a periodic measuring of the current parameters of the said process, and controlling composition of the mixed refrigerant entering the main cryogenic heat exchanger, in order to achieve the optimal process parameters. Carnot factor is used as an optimality criterion for parameters of the process. The mixed refrigerant composition is controlled by direct calculation on the basis of the current process parameters and equation of state (for example, Peng-Robinson equation of state) of the substance amount of the mixed refrigerant components required to obtain in the main cryogenic heat exchanger the temperature profile corresponding to the optimal process parameters, and to introduce the said components into the main cryogenic heat exchanger. The invention improves efficiency of the natural gas liquefaction process and, as a result, minimizes specific compressor power required for LNG production.