Collaborative writing (CW) was found to be beneficial to the students, and it has great impacts on the students’ writing outcomes. However, few studies have been investigated to see whether there are any differences in the impacts of writing between online and in-class collaborative writing. The present study analyzed 120 argumentative essays from 60 students, 30 from the virtual class and 30 from the in-class writing. The study only limits to three types of sentences written from each essay, such as simple sentences, compound sentences, and complex sentences. The study found that there were great effects of the CW on the students’ writing quality. However, there was no difference in the effectiveness of CW in both traditional classroom and online platforms. The study claims
that either platform of the language teaching, CW helps enhance students’ writing skills, and virtual classroom is also a great tool for writing activities.