A method for enabling a span-ring Optical Burst, OB, channel service, applied in an optical burst transport network which comprises a first ring network and a second ring network, a first main node in the first ring network and a second main node in the second ring network being connected via an optical fiber, the method comprising steps of: after receiving an OB channel service request which goes to a node in the first ring network and is dropped at a node in the second ring network, sending, by the first main node, a span-ring service request to the second main node to request a bandwidth resource for the OB channel service; after receiving the span-ring service request, configuring, by the second main node, a bandwidth map for the OB channel service, and sending a span-ring service response to the first main node, wherein the bandwidth map carries sending time information of an OB packet for the OB channel service designated by the second main node for the first main node; and after receiving the span-ring service response, determining, by the first main node, a sending time of the OB packet according to the sending time information, and sending the OB packet for the OB channel service in the first ring network at the sending time and turning on an optical switch from the first main node to the second main node, characterized in that the sending time information is a time period Tt designated by the second main node which is from the time when the first main node receives the span-ring service response to the time when the first main node starts to send the OB packet for the OB channel service, and Tt is calculated according to the following equation: Tt = t 1 − t 2 − t 3 + t 4 + t 5 wherein t1 is time at which the second main node expects the first OB packet for the OB channel service to arrive at the second ring network, t2 is the time when the second main node sends the span-ring service response, t3 is the transmission time for the span-ring service response, t4 is the transmission time for the OB channel service in the first ring, and t5 is the time when the OB channel service is transmitted from the first main node to the second main node. after receiving an OB channel service request which goes to a node in the first ring network and is dropped at a node in the second ring network, sending, by the first main node, a span-ring service request to the second main node to request a bandwidth resource for the OB channel service; after receiving the span-ring service request, configuring, by the second main node, a bandwidth map for the OB channel service, and sending a span-ring service response to the first main node, wherein the bandwidth map carries sending time information of an OB packet for the OB channel service designated by the second main node for the first main node; and after receiving the span-ring service response, determining, by the first main node, a sending time of the OB packet according to the sending time information, and sending the OB packet for the OB channel service in the first ring network at the sending time and turning on an optical switch from the first main node to the second main node, characterized in that the sending time information is a time period Tt designated by the second main node which is from the time when the first main node receives the span-ring service response to the time when the first main node starts to send the OB packet for the OB channel service, and Tt is calculated according to the following equation: Tt = t 1 − t 2 − t 3 + t 4 + t 5 wherein t1 is time at which the second main node expects the first OB packet for the OB channel service to arrive at the second ring network, t2 is the time when the second main node sends the span-ring service response, t3 is the transmission time for the span-ring service response, t4 is the transmission time for the OB channel service in the first ring, and t5 is the time when the OB channel service is transmitted from the first main node to the second main node.