NOVELTY - Liquefaction of small natural gas includes purifying natural gas through purification gas compressor, feeding into first heat exchanger, cooling, feeding into second heat exchanger, and cooling to obtain liquefied natural gas (LNG); feeding into first throttle valve, throttling, adding into first flash tank, and separating nitrogen-rich gas into first flash tank top; and dividing first flash tank bottom LNG liquid phase into first stream and second stream, feeding first stream into second throttle valve, throttling to obtain LNG/natural gas, and mixing with nitrogen-rich gas.    USE - Method for liquefaction of small natural gas (claimed).    ADVANTAGE - The method is simple, and has stable device operation and no refrigerant ratio problem. The product has nitrogen content of below 1%.    DETAILED DESCRIPTION - Liquefaction of small natural gas comprises:    (A) purifying natural gas through purification gas compressor at 10-25 MPa, feeding into first heat exchanger, pre-cooling to 0-20 degrees C, preferably 5-15 degrees C, cooling through refrigerator at - -15 degrees C to - 40 degrees C, preferably - 20 degrees C to - 30 degrees C, feeding into second heat exchanger, and cooling to - 100 degrees C to - 130 degrees C to obtain liquefied natural gas (LNG);    (B) feeding into first throttle valve, throttling to 0.8-2.5 MPa, adding into first flash tank, and separating nitrogen-rich gas into first flash tank top;    (C) dividing first flash tank bottom LNG liquid phase into first stream and second stream, feeding first stream into second throttle valve, throttling to 0.1-0.8 MPa to obtain LNG/natural gas, mixing with nitrogen-rich gas, feeding into third throttle valve, throttling to 0.1-0.8 MPa, feeding into second flash tank, and separating nitrogen-rich gas into second flash tank top;    (D) throttling second flash tank bottom liquid phase and first flash tank bottom liquid phase, feeding stream into LNG flash tank, and discharging LNG product while returning back boil off gas into second heat exchanger, feeding into compressor, and pressurizing to 0.8-2.5 MPa; and    (E) successively returning back obtained second stream into second heat exchanger to provide coolant first heat exchanger, and recycling purge gas to compressor inlet.