Formulaic sequences processing ，due to its coexistence of  integral cognitive economy  and structure and semantic comprehension complexity ，is difficult  to  measure． This  experiment  explores  the  formulaic  sequence  processing  mechanism  em- ployed by  Chinese learners of English through measuring their reaction time and error rate in judging the grammaticality of formu- laic and nonformulaic sequences． It is found out that formulaic sequences provide an unequivocal processing advantage over non- formulaic  sequences in terms of processing speed and accuracy ，that within formulaic sequences ，idiom processing speed is slower and accompanied with more errors than that of non-idioms ，showing the negative influence of structure complexity on processing ， and that the main effect  exists in the variable of language proficiency ，with higher level learners having a tendency of processing the formulaic sequence as a whole with shorter response time and fewer errors．