The phenomenon of plagiarism in coursework is common among college students. This phenomenon seriously affects the quality of higher education. The school has developed a series of homework similarity checking models to ensure the originality of English teaching coursework. The fractional differential equation method is used to classify and analyze the assignments with plagiarism suspicion. The article calculates program similarity’s fractional differential equation calculation by sequence matching algorithm in English homework. Finally, we extract AST features of similar program parts and generate spatial vectors. The research aims to find out plagiarized assignment texts by cluster analysis. Experimental research shows that the establishment of this model can assist English teachers in checking online homework. At the same time, the model can also help improve the efficiency of teachers’ homework checking.