A multicast protection method for a WDM optical network, characterized by comprising: obtaining a working path from a source node to one of destination nodes; obtaining a protection path corresponding to the working path; and repeating the above steps until working paths and corresponding protection paths from the source node to all the destination nodes are obtained; wherein if at least one working path between the source node and another destination node has been obtained, the process of obtaining a working path from the source node to the one of destination nodes comprises: selecting a shortest working path among candidate working paths from all nodes on the obtained at least one working path between the source node and another destination node to the one of destination nodes, and a source node of the shortest working path, wherein the shortest working path is a candidate working path with the lowest cost among the candidate working paths from all the nodes on the obtained at least one working path between the source node and another destination node to the one of destination nodes, and the source node of the shortest working path is such a node on the obtained at least one working path between the source node and another destination node that the candidate working path from the node of the shortest working path to the one of destination nodes has the lowest cost; and combining the shortest working path and a working path from the source node to the source node of the shortest working path into the working path from the source node to the one of destination nodes. obtaining a working path from a source node to one of destination nodes; obtaining a protection path corresponding to the working path; and repeating the above steps until working paths and corresponding protection paths from the source node to all the destination nodes are obtained; wherein if at least one working path between the source node and another destination node has been obtained, the process of obtaining a working path from the source node to the one of destination nodes comprises: selecting a shortest working path among candidate working paths from all nodes on the obtained at least one working path between the source node and another destination node to the one of destination nodes, and a source node of the shortest working path, wherein the shortest working path is a candidate working path with the lowest cost among the candidate working paths from all the nodes on the obtained at least one working path between the source node and another destination node to the one of destination nodes, and the source node of the shortest working path is such a node on the obtained at least one working path between the source node and another destination node that the candidate working path from the node of the shortest working path to the one of destination nodes has the lowest cost; and combining the shortest working path and a working path from the source node to the source node of the shortest working path into the working path from the source node to the one of destination nodes. selecting a shortest working path among candidate working paths from all nodes on the obtained at least one working path between the source node and another destination node to the one of destination nodes, and a source node of the shortest working path, wherein the shortest working path is a candidate working path with the lowest cost among the candidate working paths from all the nodes on the obtained at least one working path between the source node and another destination node to the one of destination nodes, and the source node of the shortest working path is such a node on the obtained at least one working path between the source node and another destination node that the candidate working path from the node of the shortest working path to the one of destination nodes has the lowest cost; and combining the shortest working path and a working path from the source node to the source node of the shortest working path into the working path from the source node to the one of destination nodes.