After a 220 kV transmission line is equipped with a line type terminal arrester, breaker fracture breakdown fault of 220 kV line circuit breaker is still frequent. This paper gives a detailed analysis of 220 kV circuit breaker fracture breakdown fault, and uses the theory of the steepness of the lightning wave to deduce the allowable electrical distance calculation formula between the line type or substation typr arrester and the circuit breaker fracture. When a 220 kV line is strucked by lightning, the following two conclusions can be drawn through calculation: 1) the overvoltage value of circuit breaker fracture when line type arrester is adopted on the 220 kV transmission line is 70% higher than that substation type arrester is adopted; 2) the withstand voltage of circuit breaker fracture line type arrester is adopted is 0.92 times of its overvoltage, while the fracture withstand voltage of circuit breaker when substation type arrester is adopted is 1.56 times of its overvoltage. This shows that there is no effective protection of 220 kV line type arrester on circuit breaker fracture, while substation arrester can effectively protect the fracture of circuit breaker. This paper provides basis for the modification of anti-accident measures and the modification of technical standard.