The innovative interdisciplinary integration teaching of interior design and environmental design courses results from the interaction between the development of disciplines and the needs of the times, individual aesthetic needs, and the optimization of the human habitat. Based on the STEAM teaching theory, the article analyzes the advantages of interdisciplinary integration teaching and establishes the teaching mode for interior design and environmental design courses. Students of interior design at a university were selected as the research object, and a system for evaluating teaching quality was established. The weights of evaluation indexes were solved using the rough set method, and the fuzzy comprehensive evaluation method was combined with it to conduct a thorough evaluation of the interdisciplinary, integrated teaching mode. A comparison experiment was conducted to analyze the effectiveness of the multidisciplinary integration teaching mode. After conducting the teaching comparison experiment, the mean value of the posttest scores for core literacy students in class A is 27.22 points higher than that of class B. The difference in occupational physical, mental, and behavioral literacy weighting is only 0.13%, and the overall evaluation score for the quality of interdisciplinary integrated teaching is 8.183. Introducing multidisciplinary integration teaching can improve students’ interior design abilities and help improve the quality of training in interior design and environmental design talents in colleges and universities.