In this study, I intend to diachronically examine the changing process of notation of the underlying form of syllable-final consonant 'ㅅ' in the neutralization of 'ㅅ' and 'ㄷ'. In the previous studies, it is commonly understood that 'ㅅ' and 'ㄷ' had been written in the mixture as 'ㅅ' and 'ㄷ' neutralize each other, but 'ㅅ' started being primarily notated after the 18th century. However, there needs a detailed examination of the mixed description. Particular in Hangeul Ganchal, 'ㅅ' and 'ㄷ' do not show the same mixing dynamics as seen above in the process where syllable-final consonant 'ㅅ' and 'ㄷ' are written in the mixture. That is, the underlying form of syllable-final consonant 'ㄷ' is mixed with 'ㅅ' in writing in the neutralizing process with it, but the underlying form of syllable-final consonant 'ㅅ' is primarily written in the neutralizing process with 'ㄷ', though the mixture with 'ㄷ' in writing happens intermittently. In this respect, I aimed to look into the changing process of notation of the underlying form of syllable-final consonant ‘ㅅ’ for the case of a bound noun ‘것’ and a common noun ‘옷’(衣) in Hangeul Ganchal during the 16th and 20th centuries. Therefore, I found more than 280 '것{#, +C}' and 100 '옷{#, +C}' in Hangeul Ganchal of the 16th and 20th centuries. However, I found no 걷’ type and ‘옫’ type, which are the forms of ' ㄷ', but ‘것’ type and ‘옷’ type, which are the forms of ‘ㅅ’. Judging from this, I could know that after the 16th century during which 'ㅅ' and 'ㄷ' were neutralized, 'ㅅ' and 'ㄷ' appeared to be written in the mixture and the underlying form of syllable-final consonant 'ㅅ' didn't show mixed writing with 'ㄷ' types. Therefore, it can be concluded that most of the mixed notations resulted from the mixture of underlying form syllable-final consonant ‘ㄷ’ with underlying form syllable-final consonant ‘ㅅ’. (Chungnam National University)