The work aims to design an A/C internal unit packaging machine controlled by PLC, so as to achieve the goal that machine replaces manpower. By analyzing the process of producing packages for A/C internal unit, SolidWork software was used to respectively establish 3D models with respect to positioning of A/C internal unit, taking foam pad, supplying foam pad and packaging box and boxing, etc. Meanwhile, the mechanical design of the parts comprising all the mechanisms was made. S7-200 SMART PLC was adopted to control the coordinated operation of stepping motor and cylinder of each mechanism, so as to achieve the automatic packaging of A/C internal unit. The packaging machine could automatically package A/C internal units of three different specifications. It is concluded that the packaging machine has solved the problem of automatic packaging of A/C internal unit, which has achieved the goal that machine replaces manpower and improved the production efficiency. Moreover, the packaging machine can package A/C internal units of various specifications and it has broad application prospects.