The goal of this paper is to study Korean college students` collocation knowledge of English adjective synonyms. Three pairs of synonymous adjectives big/huge, blank/empty, complete/perfect were selected and tested. The subjects were a total of 50 college students. The results are as follows. First, the average score was as low as 50.67%. Second, there was a somewhat weak positive correlation(r=.475) between college students` general English knowledge and English adjective + noun collocation knowledge. Third, the subjects` scores were not in accordance with the actual use of native English speakers. For example, the score of huge cost was only 28% even though it is a very common expression. Fourth, the subjects` scores were much lower in the case where both adjectives are eligible (higher than 60%) than the case where only one adjective is eligible (lower than 40%). These results suggest that EFL students need to learn English with focus on collocations, not individual words.