A cross-chain transaction method and apparatus. For any node on a first blockchain of blockchains on which a plurality of associated transactions occur, after receiving an association transaction from a consensus node, the node needs to determine, based on an identifier of an anchor transaction included in the association transaction, whether the anchor transaction is a valid transaction. If the anchor transaction is a valid transaction, the node writes a transaction that occurs in the first blockchain into the first blockchain based on identifiers of the blockchains on which the plurality of transactions occur, to ensure that the plurality of associated transactions on the plurality of blockchains are successfully submitted simultaneously.