Coral and its endosymbiotic algae, Symbiodinium is one of the well-known mutualistic symbiosis. Symbiodinium have different genotypes and adult coral often associate with one dominant type, whereas coral juveniles can acquire multiple different symbiont types. Changes of Symbiodinium genotypes in adult corals were observed following heat stress. In juveniles changes occur through the development of the corals, potentially providing them more chances to cope with various environmental stresses. However, current understanding focuses more on the qualitative change of Symbiodinium types in juveniles, and the knowledge of the quantitative change of Symbiodinium communities in response to thermal stress is relatively limited. In this study, we investigated how the Symbiodinium communities quantitatively changed under high temperature (31℃) compared with control temperature (28 ℃) in juvenile Acropora tenuis over 2 months using qPCR. Survival of corals was monitored at 2 weeks, 1 month and 2 month time. Our results showed that in both temperature conditions, juvenile A. tenuis did not show a significant mortality, while the quantification of Symbiodinium clades highlighted distinct community composition after 2 months. Here we will present these results and discuss on how ocean warming potentially affect dynamics of symbiont communities in coral juveniles.