Abstract: The CBL1 protein is an important class of calcium signal proteins, which can response to drought, low temperature, high pH and other environmental stress. The differential scanning calorimetry was applied to study thermal properties of CBL1 protein from Populus during -30℃ to 0℃ and 20℃ to 95℃. It was found that although the CBL1 protein from Populus played a role in response to low temperature stress, but itself did not have frost resistance, meanwhile in the melting process, the ice content and temperature fitted exponential relationship. During the heating process, the irreversible denaturation temperature of CBL1 protein was about 81.6℃, meanwhile the performance of the entropy and enthalpy decreased in increments when it was below the denaturation temperature, and once climbed up to the denaturation temperature, the entropy and enthalpy increased rapidly, which showed a high thermal stability of CBL1 protein from Populus.