Disclosed are a method for detecting a malicious node in a block chain and a block chain. The method comprises: a notary node acquires an authenticated verification message, a first verification message from a first sending node, a second verification message from a second sending node and a third verification message from a receiving node; and the notary node determines a malicious node among the receiving node, the first sending node and the second sending node according to the authenticated verification message, the first verification message, the second verification message and the third verification message. When the method is used in Fintech, the malicious node among the receiving node, the first sending node and the second sending node may be determined by verifying the consistency relationship between a ciphertext message declared by each node and an authenticated ciphertext message.