A system for transmitting a multicast service, comprising: a first multicast ring (210, 310, 410, 710), comprising a first node (211, 311, 411, 711), a second node (212, 312, 313, 412, 414, 712), and at least one third node (213, 214, 313, 314, 413, 414, 713, 714); and a second multicast ring (220, 320, 330, 420, 430, 720), connected to the first multicast ring (210, 310, 410, 710) through the first node (211, 311, 411, 711) and the second node (212, 312, 313,412,414,712); wherein each of the first node (211, 311, 411, 711) and the second node (212, 312, 313, 412, 414, 712) comprises: a first port and a third port, configured to receive and forward a multicast service received on the first multicast ring (210, 310, 410, 710); and a second port (2, 4), configured to: when serving as an active port, forward the multicast service received from the first multicast ring (210, 310, 410, 710) to the second multicast ring (220, 320, 330, 420, 430, 720); when serving as a standby port, block forwarding of the multicast service received from the first multicast ring (210, 310, 410, 710) to the second multicast ring (220, 320, 330, 420, 430, 720), and do not receive the multicast service forwarded by the second multicast ring (220, 320, 330, 420, 430, 720), wherein the second port (2, 4) of the first node (211,311,411, 711) is an active port, and the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) is a standby port; wherein the first node further keeps the second port (2, 4) of the first node (211,311,411, 711) as an active port, when a failure is detected by the first node on the second multicast ring (220, 320, 330, 420, 430, 720); and wherein the second node further switches the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) from a standby port to an active port, when the failure is detected by the second node on the second multicast ring (220, 320, 330, 420, 430, 720); wherein the multicast service forwarded by the second port (2, 4) of the first node (211,311,411, 711) is transported on the second multicast ring(220, 320, 330, 420, 430, 720) in a first direction when the second port (2, 4) of the first node (211,311,411, 711) serves as an active port, and the multicast service forwarded by the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) is transported on the second multicast ring (220, 320, 330, 420, 430, 720) in a second direction when the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) serves as an active port, the first and second direction being opposite. a first multicast ring (210, 310, 410, 710), comprising a first node (211, 311, 411, 711), a second node (212, 312, 313, 412, 414, 712), and at least one third node (213, 214, 313, 314, 413, 414, 713, 714); and a second multicast ring (220, 320, 330, 420, 430, 720), connected to the first multicast ring (210, 310, 410, 710) through the first node (211, 311, 411, 711) and the second node (212, 312, 313,412,414,712); wherein each of the first node (211, 311, 411, 711) and the second node (212, 312, 313, 412, 414, 712) comprises: a first port and a third port, configured to receive and forward a multicast service received on the first multicast ring (210, 310, 410, 710); and a second port (2, 4), configured to: when serving as an active port, forward the multicast service received from the first multicast ring (210, 310, 410, 710) to the second multicast ring (220, 320, 330, 420, 430, 720); when serving as a standby port, block forwarding of the multicast service received from the first multicast ring (210, 310, 410, 710) to the second multicast ring (220, 320, 330, 420, 430, 720), and do not receive the multicast service forwarded by the second multicast ring (220, 320, 330, 420, 430, 720), wherein the second port (2, 4) of the first node (211,311,411, 711) is an active port, and the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) is a standby port; wherein the first node further keeps the second port (2, 4) of the first node (211,311,411, 711) as an active port, when a failure is detected by the first node on the second multicast ring (220, 320, 330, 420, 430, 720); and wherein the second node further switches the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) from a standby port to an active port, when the failure is detected by the second node on the second multicast ring (220, 320, 330, 420, 430, 720); wherein the multicast service forwarded by the second port (2, 4) of the first node (211,311,411, 711) is transported on the second multicast ring(220, 320, 330, 420, 430, 720) in a first direction when the second port (2, 4) of the first node (211,311,411, 711) serves as an active port, and the multicast service forwarded by the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) is transported on the second multicast ring (220, 320, 330, 420, 430, 720) in a second direction when the second port (2, 4) of the second node (212, 312, 313, 412, 414, 712) serves as an active port, the first and second direction being opposite.