Abstract: The information redundancy of primary equipment in Substation Automation System (SAS) is caused by double IEDs which integrated protection and monitoring functions in 220kV and above system. So the strategy that maps middle data to real data of double integrated IEDs without changing the structure of current SAS is put forward to s realize the filtering of information redundancy. This method has been implemented in CSC2000 (V2) SAS which is applied in the Tangshan 220kV Guojiatun digital substation successfully.