Carbon accounting helps guide governments in formulating emission reduction policies, promoting lowcarbon economic development, and fostering international cooperation to address climate change challenges. Currently, the carbon accounting mechanism faces issues such as underreporting, concealment, and falsification of corporate carbon emission data to reduce the cost of carbon quota clearance, as well as insufficient regulatory efforts among participants, leading to a lack of authenticity and accuracy in accounting, and difficulty in protecting corporate data privacy. To address these issues, this paper proposes a privacyprotecting carbon accounting model based on blockchain technology. Firstly, by integrating with blockchain, data is made public, transparent, and traceable by uploading it onto the chain. Secondly, to address privacy concerns of data on the chain, this paper employs a homomorphic encryption system to encrypt the data. Additionally, digital signature technology is introduced to allow multiple participants to sign the data for mutual confirmation. Finally, this paper designs a ciphertextbased comparison protocol, expanding the auxiliary functions of the carbon accounting management system, and providing a secure data comparison function between enterprises. Theories and experiments demonstrate that this solution can efficiently and securely achieve carbon accounting.