To solve the problems of users’ private key security, this study proposes a user-oriented and practical private key protection framework by combining secret sharing and edge computing mode. Based on this framework, it designs a private key protection scheme for the SM2 public-key cryptographic system. In this scheme, a user’s SM2 private key is divided into two shares via a secret sharing scheme and kept by the user’s device and the edge server respectively. The public-key cryptographic task requested by Web3 applications is executed cooperatively by the user’s device and the edge server without having to recover the original private key. After the user’s device or the edge server is attacked, a key updating protocol will be executed among them to update the private key shares and scrap the one that may have been leaked. Experiment results show that the computing time of the new scheme is acceptable for common devices (smartphones, laptops, etc.) in the real world.