The present disclosure discloses a method, apparatus, node, system for blockchain-based identity authentication. The method includes: receiving an authentication request sent by an authenticated party node; in the case that it is determined that the identity information of the authenticated party node and identity proof publishing node, and a digital signature of the identity proof publishing node on the identity information of the authenticated party node have been written into a blockchain, verifying the digital signature according to a public key of the identity proof publishing node; after the digital signature passes the verification, determining whether the authenticated party node has mastered a private key corresponding to the public key of the authenticated party node; and in the case that it is determined that the authenticated party node has mastered the private key, it is determined that the authenticated party node passes the identity authentication.