In order to investigate the effect of water extract from Flos Chrysanthemi Indici (WE-FCI) on the heat tolerance of organism, drosophila melanogaster was feed with 1%, 3%, 5%, 7% WE-FCI, respectively, to conduct heat exposure test and heat acclimatization test. The results showed: In heat exposure test, WE-FCI could significantly prolong the median lethal time (LT₅₀)、the average survival time (T)and the maximum survival time (T_max) of female drosophila melanogaster_, which were compared to HE-control group; When the concentration of WE-FCI was ≥3%, it would improve the heat tolerance of male drosophila melanogaster. Under heat acclimatization test, different concentrations of WE-FCI influencing the drosophila melanogaster’s heat tolerance index had no obvious regulation; In the whole, 3% WE-FCI could stably improve the LT₅₀, T and T_max of drosophila melanogaster. It suggested that FCI can increase the heat tolerance of drosophila melanogaster exposed to high temperature environment, which can provide scientific basis for the research and development of FCI heat-relieving drink.