Multimedia has changed traditional white-blackboard lecture forever and reformed continually the forms and presentation of materials. In this paper, we propose an online marking system. The realization of this system will help improve working efficiency of marking papers, reduce potential cheating and facilitate the teacher storage and analysis students' examination papers. The system is realized based on B/S structure (Browser/Server structure) which will increase the flexibility of online marking as long as the teacher accesses to the Internet. In the proposed system, some functions in OpenCV have been introduced in procedure such as image segmentation, image enhancement and image rectification to make sure the picture which is shown to the reviewer is correct and clear. In database design of the system, we have fully considered the security issues and the data scalability, we adopt SQL server 2005 as our primary database to ensure comparable large storage capacity and throughout capacity. The system has realized online marking and the storage streamlined, which will improve teacher's work efficient and provide a reference for learning schedule and a feedback to teaching achievements.