To propose an assistant decision-making support method based on ontology, aiming at the problem of knowledge representation and reuse in packaging design area. A quintuple packing design knowledge model was built firstly, and then the packaging design semantic ontology model was designed, which was based on packaging design knowledge such as design cases, design resources and design elements. The Jena reasoning rules for packaging design assistant decision making were constructed, and lastly SPAQRL was adopted to query the underlying knowledge based on ontology. In order to show the feasibility of the method, the paper gave a case study which described the fulfillment of decision making service in four layers including the presentation layer and decision-makers. The result showed the method was capable of assisting decision making during the packaging design process. This study provides methods and technology for improving the intelligence of packaging design decision support.