The invention belongs to the technical field of a power system, and particularly relates to a microgrid relay protection device and protection method. Each path of signal acquisition and distinguishing system in the device sequentially comprises a first switch, a sampling circuit, a second switch, a first retaining circuit, a third switch, a first branch, a second branch, a subtraction circuit, anabsolute value operational circuit, a voltage comparison circuit, a sixth switch and a controller according to an electrical signal transferring direction, wherein the first branch comprises a fourthswitch and a second retaining circuit, the second branch comprises a fifth switch and a third retaining circuit, and the first branch and the second branch are connected in parallel. The method is used for controlling the time sequence of each switch, monitoring total frequency and continuous frequency of an input voltage larger than a threshold value in the voltage comparison circuit and outputting a trip control signal. By the device and the method, switching between two modes can be achieved, meanwhile, the device and the method have rapid break protection timeliness, the problem of signalswitching missing also can be prevented, and the problem that an unsteady-state distortion noise signal of a power grid is judged to be a switching signal by mistake can be prevented.