This paper examines Chinese students’knowledge ofderivational suffixation,word association as well as vocabularysize.Results show that students master noun suffixes better thanadjective suffixes.As to word associations,students producedmore syntagmatic associations than paradigmatic associations.This research also found a significant correlation betweenvocabulary size and paradigmatic associations.At last,byinvestigating the relationship between the three aspects of wordknowledge,the author tries to apply this relationship to secondlanguage acquisition.