Abstract: Based on the on-line monitoring data of 5 ocean environmental buoys in Mirs bay in the 2015, this paper analyzes the temperal and spatial characteristics of chlorophyll-a in the coastal waters of Mirs bay and its corrections of the main water quality parameters. The results show that the maximum value of chlorophyll-a in winter is 82.23 μg/L, which is the lowest one compared with the other three seasons. Affected by the hydrodynamic environment and land-based emissions, it was perennially higher in the Sha Tau Kok Sea zones than the other zones of Mirs bay. The results of Pearson correlation analysis showed that the chlorophyll-a concentration was significantly proportional to water temperature, but when comparing the chlorophyll-a concentration with salinity, there was no obvious correlation between them. Overall, the spatial and temporal distribution of chlorophyll-a concentration is influenced by the land runoff, the external waste loads, the aquaculture environment and so on.