[Objectives]Temperature adaptation is very important for the survival of animals. However, there is still a lack of correlational research on the temperature adaptation of ectothermic animals such as fish. Perccottus glenii can survive for several days in frozen environments, and Symphysodon aequifasciatus is a widely-reared tropical ornamental fish. These two species of fish were regarded as the representative of the cold-water fish and tropical fish in this study. [Methods] To investigate their temperature tolerance, we performed linear regression on the percentage of experimental fish that were out of balance at different temperatures and then interpolated the temperature value corresponding to 50% individual imbalance to obtain the critical temperature of the two fish species. We also measured their heart rate across the temperature gradient. Then the cardiomyocytes of P. glenii and S. aequifasciatus were acutely isolated, and whole-cell patch-clamp and temperature control techniques were also used to explore the electrophysiological characteristics of voltage-gated sodium channels in two kinds of fish cardiomyocytes at different temperatures (15 ℃, 20 ℃, 25 ℃, and 30 ℃). PatchMaster was used to record the original data, and Igor Pro 6.37 was used to fit the data and draw curves, the significance was inspected using one-way ANOVA. [Results] The temperature tolerance ranges of P. glenii and S. aequifasciatus were﹣2.0 to 27.4 ℃ and 13.1 to 39.3 ℃, respectively. The heart rate of P. glenii increased steadily from 0 ℃ to 19 ℃, reached the highest at 19 ℃, and then decreased gradually (Fig. 3), which was consistent with the electrophysiological characteristics of the voltage-gated sodium channel in the myocardial cells:voltage-gated sodium channels in the cardiomyocytes of P. glenii had the highest peak current (normalized current:﹣0.93 ± 0.11) and the highest opening probability (G50:﹣29.48 ± 0.33 mV) at the temperature of 20 ℃ (Fig. 4 and Fig. 6). The heart rate of S. aequifasciatus increased steadily from 14 ℃ to 31 ℃, which was consistent with the electrophysiological characteristics that the peak current and open probability of voltage-gated sodium channel in cardiomyocytes increased with the increase of temperature within the experimental range between 15 ℃ and 30 ℃, and voltage-gated sodium channels of S. aequifasciatus had the highest peak current (normalized current:﹣1 ± 0) and the highest opening probability (G50:﹣31.46 ± 0.33 mV) at 30 ℃ (Fig. 5 and Fig. 6). [Conclusion] These results indicate that the temperature response of the heart rate and voltage-gated sodium channel complex current in the cardiomyocytes of these two fish species is closely related to their own temperature tolerance range and the temperature of their native habitat. Therefore, the voltage-gated sodium channel of fish cardiomyocytes may play an important role in the temperature adaptation process of the two species of fish and maybe a key protein in the temperature adaptation of the two species of fish.