對許多學生來說,完成商用英文寫作是一項艱鉅的任務。為了協助學生克服此困難,本研究透過兼具教學與通訊的社會學習網絡平台──CoCoing.info,不僅提供學生相互觀摩與學習的數位空間,平台內建的多媒體階層圖功能,更讓學生能夠將所思所想結構化、可視化的呈現出來,以利寫作時有所參照。本研究使用準實驗研究法,並採用了桃園市某大學59名大學生作為研究對象──實驗組32名、對照組27名。實驗為期十六週,每週教學兩小時,以探討多媒體階層圖對商用英文寫作之成效、多媒體階層圖分數與商用英文寫作表現間之關係以及同儕評量結果與教師評量間之關係。研究結果顯示,雖然實驗組在多媒體階層圖的輔助下,其商用英文寫作表現顯著優於對照組,但多媒體階層圖分數與商用英文寫作成績間並無相關性,所以本研究進一步分析後,發現多媒體階層圖之階層數與商用英文寫作之段落數間具有顯著相關性,而教師評量多媒體階層圖之成績與同儕評量之結果間亦具有顯著相關性。因此,綜合以上發現,本研究歸納出了多媒體階層圖對寫作之效益及同儕評量成效等重點,並希望這些研究成果與建議能對相關領域之學者在進一步的研究探索與發展中有所助益。;For many English as a second language students, Business English writing is a challenging task. To help students overcome this difficulty, this research used CoCoing.info, a social learning network platform that combined education and communication. It not only provided a digital learning space for students to observe and learn from each other, but also the function of multimedia hierarchical chart allowed students to present their thoughts in a structured and visual way, so that they could refer to them in writing. A total of 32 hours of experimental study with 59 students from a university in Taoyuan City was adopted of which 32 students were grouped as the experimental group and 27 students as the control group to explore the effectiveness of multimedia hierarchy charts in business English writing, the relationship between the scores of the multimedia hierarchy charts and the business English writing scores, and the relationship between results of the peers’ assessment and teachers’ assessments were involved and evaluated for the study. The results showed that although the experimental group’s business English writing performance was significantly better than the control group with the aid of the multimedia hierarchy chart, there was no correlation between the scores of the multimedia hierarchy chart and the business English writing scores. Thus, after further analysis in this study, we found there was a positive correlation between the number of levels in the multimedia hierarchy chart and the number of paragraphs in business English writing, and there was also a moderate positive correlation between the results of the teacher’s assessment and the peer assessment. Therefore, based on the above findings, this study summarized the research conclusions and recommendations of the effectiveness of multimedia hierarchy chart on business English writing and the effectiveness of peer assessment, which I hoped can be used for reference by related researchers in the future.