This research aimed to 1) study the factors that affect third-year undergraduate students' creative thinking ability at Baise University, 2) develop an instructional model based on design thinking and brainstorming, 3) compare third-year undergraduate students' creative thinking ability before and after using the instructional model based on design thinking and brainstorming. The sample group was 45 third-year undergraduate students at Baise University. The research Instruments were 1) an interview form about factors that affect the development of third-year undergraduate students' creative thinking ability, 2) a questionnaire about factors that affect the development of third-year undergraduate students' creative thinking ability, 3) lesson plans, 4) a creative thinking ability test 5) an interview form about opinions on teaching 6) an observation form about students' behavior. This study analyzed quantitative data through descriptive statistics, frequency, percentage, means, and standard deviation. For dependent samples, t-tests were used to analyze the different scores of undergraduate students before and after using the instructional model. Qualitative data were analyzed through content analysis. The research results were 1) the factors affecting undergraduate students' creative thinking ability include environmental factors (family, school, and society) and personal factors (personality traits, motivation, attitude, and emotional state), 2) the four components of the instructional model are principle, objective, learning process, and result, 3) after implementing the instructional model, the post-test scores of undergraduate students' creative thinking ability significantly increased, with a statistical significance of 0.01.