Abstract: This study compares the syntactic complexity of a group of College Non-English Major English learners' written language in argumentative writing in one year, and analyzes the relationship between the objective syntactic complexity dimensions and the subjective artificial score. Results show that there are differences in the syntactic complexity of English learners at different levels. The indexes of syntactic complexity are related to the number of complex nominal phrases in each sentence, the number of paratactic phrases in each T unit and the number of paratactic phrases in each sentence.