As Artificial Intelligence (AI) technology is developing rapidly, the application field of AI corpora in college business English teaching has been enlarging step by step, especially in language expression practice. This paper concisely introduces the basic concept and technical background of AI corpora, and their advantages in enhancing the business English expression ability of students, optimization of learning resources, and personalized learning experiences. It elaborates on the application of AI corpora in classroom instruction, including corpus analysis, expression practice, and instant feedback, based on some teaching instances. The results show that AI corpus-based training can significantly improve the business writing, oral communication, and cultural adaptability performance of students. This provides both practical proof and theoretical basis for wider integration of AI technology in future business English teaching syllabuses.