Currently, one of the approaches that was widely used in efforts to prevent shrimp disease was to increase shrimp immunity. The use of several natural ingredients has been tried to improve the performance of shrimp immune parameters, including the use of mangrove leaf extract and microalgae extract. In this study, supernatant extract and ethyl acetate extract from the microalgae Phaeodactylum sp were used as immunostimulant to improve the immune system function of shrimp. Microalgae supernatants and ethyl acetate extracts were mixed into the feed formula at a rate of 35% of the feed weight. The test animals were 35-day-old shrimp juvenile. Supplemented feeding was carried out for 30 days before the challenge test. During the 30-day maintenance process, hemolymph sampling was carried out every 5 days to determine the Total Haemocyte Count value and Pro-PO activity. After infection with pathogenic Vibrio, hemolymph sampling was carried out therefore there were 2 sampling points in 1 week on day 4th and day 7th. After infection, shrimp survival was recorded daily. The results showed that the addition of Phaeodactylum sp supernatant extract to shrimp feed was able to stabilize and maintain shrimp immune parameters after infection with pathogenic Vibrio bacteria.