The work aims to discuss the thinking fixation of designers in interactive evolutionary design (IED) and its causes. First, the phenomenon of designers' thinking fixation in IED was deconstructed, and the influence of human visual search mechanism and IGA algorithm mechanism on designers' thinking fixation in interactive evolution was also clarified. Strategies such as "visual stimulation strategy", "increase sample size strategy" and "increase mutation probability" were also proposed accordingly. Then, based on the Hausdorff distance algorithm, a quantitative method of thinking fixation in the interactive evolutionary design of product form was proposed; then, with the outline of a Chinese vase as an example, an interactive evolutionary system of product shape was developed under the MATLAB software platform. Finally, a comparative experiment was designed to verify it. The experimental results showed the effectiveness of the proposed strategy in alleviating the fixation of designers' thinking in interactive evolution.The proposed improvement strategy can help to improve the innovation of the design output of interactive evolutionary systems, and provide a new research perspective for cognitive characteristics of designers in interactive evolutionary design.