A phenomenon known as 'Milky Sea', an event where marine microorganisms with bioluminescent abilities rising to the surface, has occurred in the southern sea of Java for the first time. This study aimed to analyze the environmental condition during the event. This study used several open portal data, specifically from 30 July 2018, 30 June 2019, and 27 July to 4 August 2019. The results showed the correlation between sea surface temperature (SST) and the concentration of chlorophyll-a. The maximum concentration of chlorophyll-a was between 0.1-1.5mg/ m^-3 on August 1^st, followed by a decline and a resurgence on August 4th due to the decrease of SST. Several eddy currents and upwelling were discovered in Java's southern sea. However, the coastline section was only visible from 31 July 2019 to 2 August 2019, and faded on 3 August 2019. The ocean current system in the eastern of the Indian Ocean represented key factors in the distribution of chlorophyll-a and nutrients colonizing when the Milky Sea occurred.  The nutrient concentration, particularly nitrate, fluctuated during the Milky Sea event within a narrow range of 0.01-0.02mmol/ m³ and showed limited changes. During this time, sea surface temperature (SST) and the concentration of chlorophyll-a were associated with the abundance of nanoplankton around the Milky Sea area, which ranged from 0 to 1mg/ m³. The Milky Sea phenomenon is primarily driven by a decrease in SST and an increase in the concentration of chlorophyll-a and nanoplankton, with eddy currents and upwelling acting as catalysts.