In order to analyze the security of tubular bus in earthquake, taking the supported tubular bus structure in 220 kV substation as a research object, the vibration response characteristics of the structure under different seismic intensity are studied, and the principal stress at key position is calculated, by using the finite element model and time-history method. The analysis results show that the first ten natural frequencies of supported bus structure are 1～3 Hz, which are in the predominant period of seismic wave and are prone to resonance during earthquake in its structure. The maximum moment of post insulators happens at its bottom, which makes it easily to be broken. If the seismic intensity is less than or equal to 7 degree, the whole structure is safe because the tensile stress of post insulators is less than the ultimate strength of ceramic. However, if the seismic intensity is equal to or greater than 8, there will be fracture with some post insulators due to the exceeded stress, which may make the structure in danger.