The invention relates to cold energy utilization of liquefied natural gas (for short LNG) and air conditioner technology utilization, in particular to a system for using LNG to an air conditioner. The system comprises a closed type circulation system using a medium-temperature refrigerant as a working medium and a closed type circulation system using a low-temperature refrigerant as a working medium, the closed type circulation system using the medium-temperature refrigerant as the working medium comprises a second heat exchanger (2), a third heat exchanger (3), a medium-temperature refrigerant pump (6) and a third expansion power generator (9); and medium-temperature refrigerant steam is condensed into liquid in the second heat exchanger by the low-temperature refrigerant and the LNG, and then pressurized by the medium-temperature refrigerant pump (6). According to the system, cold energy of the LNG is used for air conditioner refrigeration, electric energy consumed by the air conditioner is saved, and the gasified LNG is used for pipeline network air supply, can also be used for additional power generation, and can generate more electric energy to be used for various kinds of electric equipment.