The transient electromagnetic environment of substation threatens safe operation of secondary systems in a substation.This paper analyzes the transient electromagnetic fields generated by lightning stroke and switching operations based on field tests and numerical simulations.The frequency range of switching transient electrical fields is smaller than 15 MHz

their time duration is 8 μs

the main frequency is in the range from DC to 1 MHz

and the rise time is in the range from 0.5 to 1.5 μs.The frequency range of switching transient magnetic fields is smaller than 15 MHz

their time duration is from 8 to 10 μs

the main frequency is in the range from 0.5 to 3 MHz

and the rise time is about 0.25 μs.The suggested maximum transient magnetic and electrical fields generated by switching operations are 400 A/m and 20 kV/m

respectively.The lightning transient magnetic field in substation is suggested as 1 000 A/m.The criterion for electronic system in substation in national electromagnetic compatibility（EMC）standard GB/T 17626.9-1998 is far smaller than the actual value in substation.The transient magnetic field criterion for the EMC test of electronic system is suggested as 1 000 A/m

and the transient electric field of 20 kV/m is suggested as another new criterion for the EMC test of electronic system.