The aim of the research is to find out whether the behaviours of novice designers are in association with their thinking styles, and which roles the thinking styles play in design. Based on the Sternberg's mental self-government theory for thinking styles, the study focused on the following thinking styles: legislative-executive-judicial, global-local, internal-external and liberal-conservative. 26 students from the course "product design methods and practice" at National Central University, Taiwan, are all novices in design and participated the research as subjects of experiments. Before conducting the experimental tests, the students were asked to take the questionnaire tests to identify their spatial ability and thinking style. The relation between thinking style and design behaviour were investigated through two experiments, "group-effect test" and "solo-test". Two issues were discussed in the tests - How will designers be influenced by external resources while in individual design work? And what will be the performance of the designers having different thinking styles while facing to the same task? In each test the students must solve the problem using sketch in a given scene. From the analysis results of the tests, the prognoses on the characteristic design behaviours of the designers with the different thinking styles before test were verified. We also find that some working behaviours of designers can be indeed explained based on the Sternberg's theory.