The security performance of quantum key distribution protocol mainly refers to the maximum secure key generation rate that the protocol can support under certain channel conditions. Depolarization channel is a common channel model in quantum information theory, which can effectively illustrate the disturbance of quantum states transmission in quantum channel. The security performance of BB84 protocol and device-independent protocol in depolarization channel is deduced and simulated by using quantum information theory. For the given depolarization quantum channel parameters and channel attenuation parameters, the security key rates of the two protocols under different channel transmission distances are given in combination with the decoy state scheme. The results can be used to theoretically simulate the security key generation rate under the condition of long-distance quantum key distribution, which establishes the theoretical basis for further security analysis and experimental implementation.