As like as central air-conditioning, the unit air conditioning unit has a lower cost, and the market price is much lower than that of the central air conditioning. However, the effect of interior decoration is exactly the same as that of the central air conditioner, and the beautiful and fashionable interior decoration needs are realized. Secondly, if the installation of outdoor units is limited, then several outdoor units can be stacked and stacked together, and if the installation location is not enough, it can be divided into two parts. It is installed on several small platforms. At the same time, the fuselage of the small main engine is light, which conforms to the load-bearing capacity of the small platform. Thirdly, because of its unit type, maintenance is also unit. When repairing and maintaining one air outlet, other air outlets are used as usual.