In traditional online static security analysis software for province level or larger power systems，the action influence of security automatic devices is not considered.Therefore，in some cases，the analysis result cannot correctly reflect the real situation of power system.A novel practical method of online static security analysis considering automatic device simulation for large power systems is put forward.The model maintenance burden can be considerably alleviated through custom-modeling based on adopting condition and action groups.The accurate analysis result and fast calculation speed can be well achieved by using local network topology to get changing logical nodes of automatic device post-action and partial matrix re-factorization to modify the factor table.The simulation results of practical power network show that the proposed approach can be applied online in large power systems.