The invention relates to an SDN (Software Defined Network) service chain application validity detection method. The method includes the following steps that: a first application and a second application in an SDN service chain are selected and are marked as P and Q; the action of each rule in the P is executed in a simulation manner, and the action of each rule in the P acts on the matching domain of the rules; any one rule in the Q is intersected with each rule in the P, if an intersection result is not empty, the intersection result is adopted as a new rule; if the intersection of any one rule in the Q and any rules in the P does not produce any new rules except default rules, a situation that the P application invalids the rules extracted from the Q application is marked, otherwise, a situation that the P application does not cover the rules in the Q application; and if the service chain has other applications behind the Q, the Q application is marked as a new P application, and the subsequent applications of the Q are marked as new Q applications, and detection is re-executed until the service chain has no applications behind the Q. With the detection method of the invention adopted, malicious or falsely-configured applications in the SDN service chain can be effectively detected, and the validity of the function of the whole chain can be ensured.