Conflict detection and resolution methods and apparatuses relate to the field of communications technologies. The conflict detection method includes: acquiring, by a controller, a flow path of a data flow on a network, where the flow path is used to indicate a path along which the data flow reaches an address in a destination address range from an address in a source address range through at least two intermediate nodes on the network, a first flow table rule is added to or deleted from flow tables of the at least two intermediate nodes, and the first flow table rule is any flow table rule; and determining, by the controller, whether a conflict exists according to an address range of the flow path and an address range of a security policy.