The invention relates to a method for preventing misoperation of in-situ bus protection, a misoperation preventing device, and an in-situ bus protection system. The method for preventing misoperationof in-situ bus protection includes the steps: collecting interval currents of bus protection, wherein in each slave machine, and the wiring polarities of devices CT for collecting the odd interval currents and the even interval currents are opposite to each other; multiplying the collected odd interval currents and even interval currents of the local slave machine by different coefficients respectively; and according to the odd interval currents and the even interval currents multiplied by different coefficients in the slave machine and the received each interval current of the other slave machines in the looped network, calculating the differential current to achieve differential protection. The method for preventing misoperation of in-situ bus protection connects the devices CT for collecting the odd and even interval currents in the local salve machine in a mode of opposite wiring polarity, and then performs reverse processing on the odd or even interval currents to unify the current symbols of all the intervals, thus eliminating the differential additional current caused by the power frequency magnetic field interference, effectively preventing misoperation of in-situ bus protection under the power frequency magnetic field interference, and guaranteeing safe operation of the power system.