There is currently a demand for LNG-plants with the capacity ranged from 5 to 20 t/h. The analysis showed that sufficiently efficient installations of the given capacity can be developed on the basis of the external cryogenic nitrogen expander cycle. In the course of further study it was found that when LNG-plant with the capacity up to 10 t/h is made the preference to the scheme with a turbo expander-compressor unit and pre-cooling stage of nitrogen by a refrigerating machine should be given. The minimum value of the specific energy consumption of 0,66 kWh/kg for the liquefaction of natural gas was achieved in LNG-plant at the optimum temperature of 233 K for nitrogen pre-cooling by a refrigerating machine. At JSC «Cryogenmash» for a customer was developed a project of LNG-plant with the capacity of 7 t/h which uses the optimal mode and circuit parameters found in the course of minimization of the specific energy consumption for the liquefaction of natural gas. JSC «Cryogenmash» is already underway manufacturing and supplying the equipment of LNG-plant for the customer.