This research investigates students' performance while writing Chinese essays using an interactive online writing system. Participants include students from two seventh-grade classes of a junior high school in Taoyuan County, Taiwan. The experimental group uses the conditioned writing interactive online system, while the control group receives traditional paper-and-pencil writing instruction. Findings show that this writing system makes a significant difference in students' writing performance in the areas of "argumentation" and "organization and structure", two essential elements of Chinese essay writing. This study proposes practical applications of the online interactive writing system for junior high school students' Chinese essay writing. (Contains 12 figures and 5 tables.)