A bus protection method for CTs connected at two sides of a bus-tie switch comprises a protection device for more than two sections of buses. The protection device acquires all bus voltages, all branch current and knife switch positions on a bus and CT current and switch positions at the two sides of the bus-tie switch; the protection device automatically calculates bus protection three-phase voltage, large-difference current and small-difference current of each section of bus, calculates bus tie interval differential current of the bus-tie switch itself and current of the CTs at two sides ofthe bus tie, judges whether the bus tie CTs have a line-breaking fault or not and selects a faulty bus or a bus to trip when fault occurs; and meanwhile, a bus tie interval differential protection logic is newly added, the difference current of CTs at the two sides of the bus-tie switch and the current magnitude of the CTs at the two sides of the bus-tie switch are calculated, and the bus-tie switch or the bus is selected to trip according to the bus voltage opening condition, the bus-tie switch difference current and the current magnitude at the two sides. The method is simple and reliable, and improves quickness and accuracy of protection and cutting during bus dead zone fault.