Research on fish biodiversit yof seagrass bed has been carried out in Indonesian waters, and the results vary between water locations.  This study aims to determine the biodiversity of fish based on seagrass density in the day and night period. This research was conducted in the waters of Tanjung Tiram, South Konawe from February to March 2018. Fish sampling based on seagrass density in the day and night period using gillnets with mesh size of 0.75, 1.25 and 1.50 inch.  Fish biodiversity found in this study consisted of 42 species from 24 families with an abundance of 1000 individuals. Fish biodiversity in densely seagrass beds was higher than low seagrass beds.Labridae family was the most doimnan fish during the daytime while at night is dominated by the family Plotosidae. The status of  fish biodiversity based on seagrass density was categorized as moderate to high and stable diversity while based on the day-night period was classified as moderate diversity with unstable to stable conditions, and the level of dominance of both was low.