This study investigated the aspects of Korean synonym knowledge of Chinese intermediate and advanced learners. To meet the goal, 10 synonym pairs were selected through pretests and three tests were developed such as O/X test, multiple-choice cloze test, and cloze test. Sixty students(twenty per each level from 4 to 6 in TOPIK) and 20 native speakers were employed. As results, (i) native speakers also checked wrong in several O/X tests indicating having wrong intuition of use of some synonyms, (ii) rough development was found in synonym knowledge following to the proficiency, but the aspect is very irregular showing discrepancy from that of native speakers. This study claimed that proficiency was not able to predict development of synonym knowledge so that explicit educational intervention would be necessary.