Concerning the challenges of complicated credential verification processes， limited credential sharing， and users' repeatedly applying for credentials during cross-department collaborative identity authentication in the digital transformation of government services， a blockchain-based cross-department collaborative identity authentication scheme for e-government was proposed. Firstly， a Verifiable Credential （VC） and its Proof of existence （VC Proof） mechanism were designed to store credential hash values and proof information on the blockchain to enable efficient multi-departmental credential verification. Secondly， an authorized credential mechanism was constructed to facilitate credential interactions between verifiers and relevant departments， thereby reducing the burden on users to repeatedly apply for credentials. Meanwhile， a smart contract-based non-interactive zero-knowledge proof technique was introduced to complete identity authentication while preserving the privacy of VCs. Experimental results show that the proposed scheme has low verification gas consumption， stabilizing at around 500 gas， while the gas consumption for contract deployment increases linearly with the scale of the contract. When the verification gas consumption is 140.55 Gwei， its throughput reaches the highest， about 7×10⁴ TPS （Transactions Per Second）， and when the verification gas consumption increases to 562.562 Gwei， the throughout drops to approximately 2×10⁴ TPS. In addition， compared to experimental results on Ethereum， the proposed scheme demonstrates better performance under the same concurrency conditions， with the average response time reduced by approximately 0.32 seconds.