Abstract: Vocabulary and grammar have always been the weak parts in the study of PSC, and they are also easily ignored by examinees. Two hundred and ninety cases of lexical and grammatical errors have been classified analyzed by analyzing 138 cases of PSC propositional speech of college students to find that most of the dialect errors are lexical errorsand that the others are mainly manifested in violation of the rules of grammatical structure or unreasonable, mostly in improper collocation, chaotic structure and unclear meaning. Effective means to solve the problem of lexical and grammatical errors of proposition speaking items are to avoid dialect vocabulary and grammar and Internet catchwords, improve emotional self-control ability, speak at an appropriate speed and master certain expression skills and improve the test results.

Key words: PSC, vocabulary, grammar, error