In this paper we propose a Marking-based Synchronized Multimedia Tutoring system (MSMT) to enhance our previous work, the Web-based Synchronized Multimedia Lecturing system (WSML), for language learning in writing skill. For non-native users, writing is usually a barrier when they are learning a foreign language. Therefore we simulate several symbols which are common use in the traditional paper-based writing correction by state-of-the-art technologies. The system not only provides an easy-to-use interface for instructors to simplify the composition editing tasks, but also provides visualized editing markings for learners to grasp the writing mistakes. A system prototype has been implemented to support ESL composition studies. An overview page that presents the system features with demonstrations can be accessed at http://english.csie.ncnu.edu.tw/OWL/.