A method for detecting loop position in an Ethernet network, includes: the Ethernet switch device learns a MAC address; in a MAC table, a first MAC address corresponds to a first port before the learning of MAC address, and the first MAC address corresponds to a second port after the learning of MAC address; if the second port and the first port do not belong to the same sub-network, an interval between a time of learning on the second port and a time of transmitting a last packet or receiving a last packet from the first port is calculated; and if the interval is smaller than a predetermined judgment threshold of host migration, it is determined that a loop exists in a sub-network connected to the second port.