In recent years, as a new type of educational resource, microclassroom continues to attract the attention of many domestic and foreign scholars and professionals due to its short, convenient, and effective features. How to improve the quality and effectiveness of English grammar teaching has always been a concern of teachers. Researchers at all stages of education are also exploring effective teaching methods in the new era through the microclassroom model. This article aims to study the English embedded grammar supplementary teaching method and apply it to the design of the microclassroom mode. This article puts forward the definition of microclassroom and English grammar and conducts related research on microclassroom and English grammar teaching. It also proposes the theory of constructivism and the analytic hierarchy process, which are effectively applied to the experimental part of this article. The experimental part is designed from four aspects: research questions, research objects, test and survey questionnaires, and experimental research process. The experimental results of this article show that the embedded oral supplementary teaching in high school English teaching is in line with students' academic conditions and teaching rules and is taught in a microclass mode. Totally, 58.97% of students believe that this mode is more beneficial for in-depth mastery of basic knowledge.