Knowledge is an important driving force for creative design. The knowledge fusion, which is formulated by knowledge from different backgrounds, is able to inspire novelty solutions to engineering design. In this paper, a design method is proposed to facilitate knowledge fusion in engineering design based on the theory of inventive problem solving (TRIZ). In order to formulate this method, the mechanism that fosters creative ideas through knowledge fusion is firstly explained, subsequently, approaches that transform the design problems in each of the above-mentioned design stages into TRIZ problems are discussed, since the standard problems in TRIZ can be solved by corresponding TRIZ methods. A design process is therefore formulated by integrating formerly discussed strategies. Moreover, its workability is verified by a case study. The advantages of the proposed method such as the expanding the searchable range of knowledge resource for TRIZ problem solving are discussed in the final section.