The Sociolinguistic Journal of Korea 26(3). 145~170. The sibilation of Korean nominal stem final coronal consonants is a common phenomenon in Korean spoken language. Many Korean speakers pronounce /patʰ-i/, /piʨ-ɨl/, /k‘oʨʰ-e/ as [paɕi], [pisɨl], [k’ose]. These are not standard Korean pronunciations. Therefore, Korean learners are supposed not to learn this phenomenon. However, a lot of Chinese Korean advanced learners acquire those pronunciations. In this paper, I try to find why the Chinese Korean advanced learners acquire this phenomenon. Unfortunately, the reason can not be found by traditional error analysis methods. It seems that this sibilation phenomenon occurs randomly and has no connection with the coronal consonants. We can only find that when nouns combine with the postposition in an adessive case this sibilation phenomenon hardly appears. I examined Chinese Korean advanced learners’ spontaneous speaking and then conducted a survey. I show that sociolinguistic elements make a great influence on this acquisition. Lastly, I discuss how to train Chinese Korean advanced learners on this Korean phonological phenomenon.