It discusses the patterns of design knowledge reuse when designers are referring the critiques of design cases during ideation. By classifying design critiques, an observational experiment and related task are made according to the “design-referring-iteration” organization. The experiment subjects are novice designers, which are divided into experimental group and control group. Different patterns of knowledge reuse are concluded by analyzing the design conception outputs and interview data of subjects. Compared to the specific knowledge in design critique, designers tend to reuse the conceptual knowledge and actionable knowledge in design critiques. The radical modify strategy is associated to the reuse of conceptual knowledge. By highlighting the conceptual knowledge in design critiques, breakthrough in original concept can be advanced, and the efficiency of knowledge reusing can be promoted.