Content and Language Integrated Learning (CLIL) has emerged as a popular approach to language education in Europe and America in recent years. The main features of CLIL are learning foreign languages while gaining professional knowledge, enhancing student thinking, and improving the understanding of culture. However, CLIL has certain limitations, which a more effective course design may address. This paper aims to use the First Principle of Instruction (FPI) theory, one of the Instructional Design (ID) theories, to design CLIL in order to improve the course. This paper has selected the Japanese CLIL course in China as an example. The target learners are 16 students of the Japanese major at the university. The subject of the course is Intercultural Education. The results indicated that the FPI-based pre- and post- questionnaires revealed significant difference, as compared to those of the Japanese proficiency test. The analyses of the proficiency test, FPI, and CLIL indicated that there is a high correlation between the test and FPI whereas there is a moderate correlation between the test and CLIL and between FPI and CLIL.