The invention discloses a system for producing liquefied natural gas by utilizing liquid nitrogen cold energy, which comprises purification equipment, a pre-cooling heat exchanger, a gas-liquid separator, a cryogenic tank, a main heat exchanger, a throttle valve, a cryogenic tank, a liquid nitrogen storage tank and a natural gas pipeline, wherein the purification equipment is sequentially connected with a hot fluid channel of the pre-cooling heat exchanger, the gas-liquid separator, a hot fluid channel of the heat exchanger, the throttle valve and the cryogenic tank, and the gas-liquid separator is connected with the cryogenic tank; the liquid nitrogen storage tank is connected with a cold fluid channel of the pre-cooling heat exchanger through a cold fluid channel of the main heat exchanger, and the purification equipment is connected with the natural gas channel. The invention has simple equipment, and can not only obtain LNG products but also obtain liquid light hydrocarbon and other high-added-value side products; and simultaneously, the process is easy to realize skid mounting, and the system is suitable for liquefying and transportation of more dispersedly distributed natural gas resources on land or sea and biogas resources on land.