A method for setting a detection frame timeout duration for detecting a loop forming point, characterized by comprising: when at least one Ethernet node (S1, S2, S3, S4) determines that a communication port keeps a connected state unchanged or changes to a non-connected state from the connected state, setting a detection frame timeout duration of the communication port to a value within a first time range; and after the Ethernet node detects that the communication port changes to the connected state from the non-connected state, setting the detection frame timeout duration of the communication port to a value within a second time range, wherein the value within the second time range is greater than the value within the first time range; wherein further comprising: when the Ethernet node receives a detection frame transmitted by itself in the detection frame timeout duration with the value of the respective first or second time range of the communication port and a port number of the communication port satisfies an isolation rule, isolating the communication port; when the Ethernet node does not receive the detection frame transmitted by itself in the detection frame timeout duration with the value of the respective first or second time range after the communication port is isolated, relieving the isolation for the communication port immediately or after a random delay, wherein, the isolation operation refers to prohibiting the communication port from forwarding data while permitting the communication port to receive the protocol data, and the non-connected state of the communication port comprises a non-operating state, a failure state or a state in which data cannot be received and transmitted; and when various Ethernet nodes of said Ethernet node, which form a closed loop, change from forming the closed loop to forming an open loop, determining an Ethernet node from the various Ethernet nodes, where its port is isolated and the port is the last port, which enables to convert the open loop to the closed loop, to be a loop forming point of the closed loop. when at least one Ethernet node (S1, S2, S3, S4) determines that a communication port keeps a connected state unchanged or changes to a non-connected state from the connected state, setting a detection frame timeout duration of the communication port to a value within a first time range; and after the Ethernet node detects that the communication port changes to the connected state from the non-connected state, setting the detection frame timeout duration of the communication port to a value within a second time range, wherein the value within the second time range is greater than the value within the first time range; wherein further comprising: when the Ethernet node receives a detection frame transmitted by itself in the detection frame timeout duration with the value of the respective first or second time range of the communication port and a port number of the communication port satisfies an isolation rule, isolating the communication port; when the Ethernet node does not receive the detection frame transmitted by itself in the detection frame timeout duration with the value of the respective first or second time range after the communication port is isolated, relieving the isolation for the communication port immediately or after a random delay, wherein, the isolation operation refers to prohibiting the communication port from forwarding data while permitting the communication port to receive the protocol data, and the non-connected state of the communication port comprises a non-operating state, a failure state or a state in which data cannot be received and transmitted; and when various Ethernet nodes of said Ethernet node, which form a closed loop, change from forming the closed loop to forming an open loop, determining an Ethernet node from the various Ethernet nodes, where its port is isolated and the port is the last port, which enables to convert the open loop to the closed loop, to be a loop forming point of the closed loop. when the Ethernet node receives a detection frame transmitted by itself in the detection frame timeout duration with the value of the respective first or second time range of the communication port and a port number of the communication port satisfies an isolation rule, isolating the communication port; when the Ethernet node does not receive the detection frame transmitted by itself in the detection frame timeout duration with the value of the respective first or second time range after the communication port is isolated, relieving the isolation for the communication port immediately or after a random delay, wherein, the isolation operation refers to prohibiting the communication port from forwarding data while permitting the communication port to receive the protocol data, and the non-connected state of the communication port comprises a non-operating state, a failure state or a state in which data cannot be received and transmitted; and when various Ethernet nodes of said Ethernet node, which form a closed loop, change from forming the closed loop to forming an open loop, determining an Ethernet node from the various Ethernet nodes, where its port is isolated and the port is the last port, which enables to convert the open loop to the closed loop, to be a loop forming point of the closed loop.