With the development of knowledge economy globalization, problem-solving ability has become a necessary basic ability for students. Researches have confirmed that STEM teaching is an appropriate approach to improve students' problem-solving ability by taking interdisciplinary problems as the orientation. However, how to design STEM teaching experiment? What is the effect of STEM teaching in improving students' problem-solving ability? In order to answer the above two questions, this study adopted literature research method and quasi-experimental research method, and selected two classes of students in a middle school as research objects to carry out an empirical study for two months. Based on measurement tools such as problem-solving attitude questionnaire, problem solving-process observation table, and STEM work evaluation matrix, this study systematically and comprehensively verified the effect of STEM teaching on students' problem-solving ability. The results showed that STEM teaching has a positive effect on students' problem-solving attitude, problem-solving process and problem-solving results. Furthermore, the evaluation dimensions and tools for students' problem-solving ability in this study can be directly applied to relevant studies for future STEM teaching researches.