In order to testify the Optimality models, preferred temperature, high avoidance temperature and high lethal thermal maxima of the common giant toad tadpoles were measured using thermal gradient apparatus. Tadpoles of this species were acclimated at different temperatures (10 ℃, 15 ℃, 20 ℃, 25 ℃ and 15.76-5.42 ℃) for two weeks. The results showed that the preferred temperature of the common giant toad tadpoles were (17.2±3.8), (18.1±3.5), (19.6±2.5) and (15.8±2.2) ℃; the high avoidance temperature of the common giant toad tadpoles were (27.6±1.9), (31.3±1.3), (32.5±0.8), (33.9±1.0) and (31.6±1.3) ℃; the high lethal temperature of the common giant toad tadpoles were (32.9±1.6), (36.5±1.0), (37.9±0.9), (38.8±1.1) and (37.2±1.3) ℃ corresponding respectively to the acclimation temperatures 10 ℃, 15 ℃, 20 ℃, 25 ℃ and 15.76-5.42 ℃. The acclimation temperatures significantly influence on the preferred temperature, the high avoidance temperature and the high lethal temperature (P < 0.001). The acclimation temperatures impose less influence on the preferred temperature than on the high avoidance temperature and high lethal temperature in tadpoles of this species. Any environmental factor, such as a diurnal pattern of temperature, that follows an approximately sinusoidal trajectory through time will exhibit a bi- or trimodal distribution. The optimality models modeled the bimodal environment as a mixture of two normal distributions sharing a common standard deviation and separated by an intermodal distance, and these models predicted that three fitness peaks would appear when the intermodal distance of the bimodally distributed temperature was 17 ℃. Results from this study fully supported the Optimality models.