In this study, we examined the quality of water and the kinds of algae and insects the Oksukchon river along the length between Kwannung and the Han river during winter. Also examined is the relation between the quality of water and the flesh water plants in several significant points along the Oksukchon river between Kwannung and the Han river. We dicovered that the gradual pollution of the quality of water in places near villages and towns resutled in a considerable change of life in water. The present quality of water shows a remarkable difference from the limnoligical report of the winter of the year 1960 which we previously reported, and a considerable change in kinds of fish and water plant since then were noticed.