Language teacher's composition rating process has become an issue of growing concern in writing research over the past three decades. It is evident that a substantial number of composition rating research have employed concurrent think-aloud protocol analysis (TAPA) as a major method of qualitative data collection and data analysis. For the previous studies that adopted the method of TAPA in exploring the composition marking process, they were mostly confined to the study on L1/L2 English language education and not much has been done specifically on L1 Chinese language education. None of the previous studies employing TAPA were conducted with a computer marking platform. In the past, researchers generally videotaped and recorded teacher participants' think-aloud protocol during the composition marking process. However, the presence of the camera put a certain amount of psychological pressure on the participant and affected his/her performance in the rating task. To address these research gaps, a camera-free, tablet-based composition marking system is developed allowing writing researchers to examine the composition marking behavior of Chinese writing teachers with the method of TAPA conducted in a tablet-assisted marking environment. The system is able to eliminate the psychological pressure on the teacher participants as in video recording and to record their process of marking compositions systematically for later analysis.