In the context of globalization, the importance of English as the primary language for international communication is self-evident. In college, English learners face various challenges such as vocabulary accumulation, grammar mastery, and reading comprehension. Among them, the size of vocabulary directly affects the improvement of English proficiency. College English vocabulary testing is an important means of evaluating students’ English proficiency, and the scientific and reasonable difficulty of the test questions directly affects the validity and reliability of the test..MATLAB simulation shows that under certain evaluation criteria, the decision tree algorithm has the vocabulary learning and test results of college English course teaching The accuracy and reliability of the difficulty of vocabulary test questions are better than ordinary methods.