The development of ChatGPT technology has made its application in the teaching field increasingly mature. This paper takes ChatGPT technology as the basis to study its important role in the cultivation of students’ English discursive ability. The description of ChatGPT, English discursive ability, and the application of ChatGPT in the teaching of English discursive ability provide theoretical support for this research. Based on the Business English course, the course design focuses on cultivating English discursive ability, and the teaching effectiveness of the course is evaluated after its implementation. Questionnaires and classroom observation were used to explore the effect of ChatGPT on students’ English critical thinking ability with the help of tools such as the Critical Thinking Emotional Tendency Questionnaire and the Critical Thinking Cognitive Skills Rating Scale. After designing and practicing the English discursive cultivation course in this paper, 74.8% of the students thought that the feedback effect of the ChatGPT teaching method was good. The average scores of the students in Classes A, B, and C taught with ChatGPT were 82.46, 80.37, and 80.06, respectively, which were greatly improved compared with Class D, which was taught with the traditional teaching method. After the teaching experiment, the mean values of the development of discursive ability were 286.82, 281.49, 283.52, 294.79, and 287.94. This significantly improved the students’ discursive emotional tendencies through ChatGPT.