Sketch is an important creative tool for product design. In the sketching process design thinking and sketch expressing promote each other, involving the interaction between designer's actions of brain, hand and eye. The sketching process can be described as a Creative Point graph. This paper proposes a computer-aided design method based on Creative Point to support sketching process. This method recognizes sketching behaviors, and distinguished Creative Points by constructing a Creative Point rule base, and refines the rule base to avoid overfitting. A Creative Point graph is also created to record the design process and support designers' sketching. Finally, a computer-aided sketch system prototype CASCP is developed using the method, which proves effective in Creative Point recognition. A sketching case using CASCP is also presented.