In order to avoid communication conflicts in DNC systems, the scheduling tactics adopting a modified guaranteed EDF algorithm to DNC systems’ numerical control (NC) programs transmission was proposed. A condition was given to guarantee all NC machines in DNC systems work continuously. A mathematic model based on the actual expending rate of NC program was established to decide the priority of NC program transformation of all NC machines. A constraint condition for two machines with neighbored priority was proposed to avoid the conflict in the scheduling times. A dynamic scheduling scheme was presented for DNC systems. The validity of the presented method is verified by the practical tests.