Amphibians are currently considered to be one of the most endangered vertebrate groups, and facing climate change and other various threats, which can affect their physiology and overall health. Temperature-dependent immunity may be particularly important to amphibian larvae survival, especially in temperate regions. However, due to the difficulty of obtaining appropriate immunological parameters in amphibian larvae, the experimental data are still scarce whether there are physiological trade-off relationships between immune function and other physiological activities in the context of increased temperatures at some specific life history stage during metamorphosis. To explore the physiological costs of accelerated metamorphosis and development process caused by arising temperatures, the variations of metamorphosis duration from Gonser stage 37 tadpoles to Gonser stage 46 toadlets of Bufo gargarizans were counted, the body and internal organ size, stress level, and immune function were measured at metamorphosis completion period from 23℃, 25℃, 27℃ or 29℃ water temperature groups, respectively. The results showed that: (1) With increased water temperatures, the metamorphosis duration was significantly shortened, the survival probability was sharply declined, and body size was significantly shrunk. In internal organs, both wet mass and length indexes of stomach peaked at 25℃ group, and showed the minimum at 27℃ group. The wet mass index of small intestine peaked at 25℃ group, and the lowest at 29℃ group, but not for its length index. (2) The percentage of neutrophils and lymphocytes, as well as ratio of neutrophils to lymphocytes did not show obvious differences among different water temperature groups. The percentage of eosinophils was greatly higher at 27℃ group than that of any other water temperature group, the percentage of basophils and monocytes peaked at 23℃ and 27℃ group, respectively, and showed the minimum at 25℃ group. (3) Responsiveness to phytohemagglutinin-P (PHA-P) peaked at 5 h after injection for all water temperature groups, and the maximal PHA-P response value was significantly higher at 29℃ group than that of any other water temperature group. The increased moderately water temperatures were beneficial for stomach and small intestine developments of toadlets, promoting eosinophil proliferation, but suppressing basophil and monocyte proliferation. Higher water temperatures greatly stimulated the responsiveness magnitude to PHA-P antigen, accompanying with reduced survival probability, but had no direct effects on stress response capacity, suggesting that the activated temporarily immunity for rapid adaptation to the terrestrial environment may be detrimental to their future survival.