Design knowledge was reused for innovative design work to support designers with product design knowledge and help designers who lack rich experiences to improve their design capacity and efficiency. First, based on the ontological model of product design knowledge constructed by taxonomy, implicit and explicit knowledge was extracted from some design cases. The design knowledge was expressed using a constructional organization. With the knowledge map, design knowledge was illustrated to help novice designers reconstruct specific design cases, thus, encouraging innovative design. Four groups of designers were invited to participate in an experiment for the design knowledge map system. The experiment results verified the effectiveness of the method.