In recent years, the challenges and lack of progress in writing argumentative essays in English have posed a pedagogical challenge for Chinese university students. To address this issue, this paper adopts an action research pedagogy and implements a 10-week intervention aimed at teaching argumentative writing based on the Toulmin model of argumentation. The instructional process followed a holistic-to-specific approach, encompassing the following three stages: (1) introduction of the general model, (2) instruction on the main dimensions of argumentative elements, and (3) teaching of the subdimension of argumentative elements. Data collection for this study included teacher-teaching diaries, students' interviews, and four writing scores. Both paired-sample t-tests and repeated measures analyses were conducted, revealing significant improvements in students' overall performance and the quality of argumentative elements across the different stages. This paper provides a comprehensive discussion on the impact of this whole-to-detail approach to teaching argumentation on the development of argumentative essay writing skills.