A school-based curriculum using backward design is seen useful in improving Chinese students’ core competence. This study examines this assumption to see if a STEAM school-based curriculum designed using backward theory as a base can help improve Chinese students’ core competence in high school data of curriculum material, students’ products of learning the curriculum, and teachers’ evaluation of what students learn. The results show that the positive relationship exists between the STEAM school-based curriculum and the development of students’ core competence. However, while students show development in understanding mathematics and science, sense of safety and perseverance, national identity, and international communication, their performance needs to be improved to strengthen critical thinking, humanistic feelings, and social participation. In addition, the prototypes students created show excellent performance as measured by (1) mathematics and science understanding, (2) engineering, (3) artistic design, and practicality, the prototypes as measured by cost needs to be improved.