A method and a device for synchronizing network data flow detection status are provided. The method includes: a status synchronizing server receives a first request sent by a first security device node, where the first request carries a first flow entry of a first data flow that is currently detected by the first security device node; determines first network data flow detection status corresponding to the first flow entry; sends a first response to the first security device node, where the first response carries the first network data flow detection status. A security device node requests previous network data flow detection status of a data flow from a status synchronizing server so as to synchronize network data flow detection status, thereby allowing the security device node to detect a network attack in a more accurate way and improving network system security.