With the increase of international academic communication, the mission of English teaching should serve for the specific purpose of helping the students’ academic study. For teachers in universities of Science and Technology, though experts in language, lack in subject knowledge. How to instruct students to write an academic article has been a great challenge to English teachers. Based on learners' need analysis, this paper proposes ESP course for students of science and engineering and explores the effectiveness and specific implementation of PBL (project-based learning) in developing academic writing skills. In accordance with the concept “learning by doing”, PBL is mainly about helping students solve the disciplinary problem in projects and aiming at developing students’ autonomous learning and team cooperation. The results of writing tests, class participation and interviews with students all show PBL can be effectively applied in the teaching of academic writing, therefore enhance students’ academic language competence. Yet, how to assess and revise those academic writing is still an arduous task for English teachers without disciplinary knowledge in science and engineering.