Teacher practical knowledge is one of the important influencing factors for teacher professional development. This study takes college English teachers as the subjects, and through qualitative research methods, collects data such as interviews, classroom observations, teaching logs, and teaching courseware to examine their development of practical knowledge after participating in the community of practice, and explores the path of professional development of college English teachers under the background of the modernization of education. The study found that after the experiment, the subjects fully affirmed the role of information technology in promoting teaching and learning, and their practical knowledge level was improved. The problems in teaching design, classroom implementation, and post class reflection were all improved, but no significant changes were found in teacher concepts, knowledge foundation, and teaching practice. Overall, the development of practical knowledge among teachers is influenced by various factors such as teachers themselves, work environment, and external support. Focusing on the practical knowledge research of teachers in the context of educational modernization has certain enlightening significance for teacher development, school management, and educational informatization construction.