In view of the frequent damage of circuit breaker caused by lightning in the air insulated switchgear(AIS) substation in recent years, the actual 500 kV AC substation-transmission line model considering the power frequency voltage and induced voltage is established in the electromagnetic transient program EMTP, then the overvoltage level of circuit breaker under different conditions is simulated, and the reason which causes the damage of circuit breaker is analyzed. Then a comparison of lightning protective effects between two different schemes is made. The results show that, the overvoltage caused by the lightning when circuit breaker is open is the main reason that leading to the insulation breakdown and damage of the circuit breaker. For lines with voltage levels of 500 kV or above, the intrusive overvoltage of circuit breaker is from shielding failure more serious than that from the back striking. The effective protective method of the circuit breaker under lightning is installing arrester without-gap at the circuit side of circuit breaker, and the method in relavent regulation should not be directly applied to determine the installation location of substation arrester, which could be determined after simulation. The results proposed in the paper can be used as reference to the actual engineering.