A method for computing a frequency slot channel, a path computation element and a node are disclosed. The method includes: when a frequency slot channel needs to be established, an ingress node sending to a path computation element a path computation request message which carries spectrum resource information needed for establishing the frequency slot channel; according to the received spectrum resource information sent by the ingress node, the path computation element computing out the frequency slot channel by combining of topology information of a network and spectrum resource information of each node in the network. The path computation element includes a receiving module and a computing module. When working as an ingress node in a process of establishing a frequency slot channel, the node includes a message construction module and a sending module.