Lee Hwajin The goal of this study is to examine the description of ‘phonological fluctuation’ and to confirm adequacy of examples in high school textbook. The explanation of current Korean grammar textbook is focused on synchronic phonological phenomena. However various type of phonological environments that represent synchronic phonological phenomena are not proposed apparently. In consequence, the learners do not accept the principle of phonological phenomena in simple way. Firstly, I analyzed the various type of phonological fluctuations are presented in the textbook. Despite the adequacy in general description of the phonological fluctuations, there are issues in the classification of some phonological fluctuations - initial law, ‘Sait-sori’ phenomena, syllable coalescence, and S-deletion. Secondly, I confirmed the examples for the explanation are presented in the each section of textbook. There are only few examples that provide the insufficient explanation in the textbook. Therefore it needs to describe the phonological fluctuations with more consistent and diverse examples for the learners.