The invention discloses a relay protection method for cascade switching station tie lines. Longitudinal overcurrent protection is configured for the tie line interval of adjacent switching stations as main protection to tie line faults; in case of a fault, after the longitudinal overcurrent of a power supply side corresponding to the fault point is activated and when no longitudinal overcurrent start blocking signal of a load side is received, a period of set time is delayed and confirmed, and then action is performed and a switch on the local side is tripped; meanwhile, a shunt tripping signal is transmitted to a switching station protector on the load side; when the load side corresponding to the fault point receives the shunt tripping signal of the power supply side and the longitudinal overcurrent on the local side is not activated, a period of set time is delayed and confirmed, and a switch on the local side is tripped, and consequently, fault isolation is completed. For the cascade connection mode of 10kV switching stations in urban areas, the relay protection method for the cascade switching station tie lines is used for effectively solving the frequent override tripping phenomenon of 10kV distribution networks in the urban areas in the connection mode, and therefore, the fault range is prevented from expanding in case of accidents and the reliability and safety of 10kV power supply systems in the urban areas are improved.