The invention discloses a distributed topological method for constructing K channel connectivity in a cognitive AdHoc network. The method mainly settles problems of secondary user network disconnection and mutual interference of secondary users when a plurality of main users occupy a channel in prior art. The distributed topological method comprises the realizing steps of 1, broadcasting a HELLO package twice by each node in the network, receiving the HELLO packages of an initial adjacent node, and establishing a local two-hop topological subgraph; 2, constructing a shortest path tree based on the local two-hop topological subgraph, and constructing a local generation subgraph which can ensure sub-user connectivity according to the shortest path tree; 3, adjusting an emission power according to a one-hop adjacent node in the local generation subgraph and determining the logical adjacent node of each node; and 4, forming a full network topology by all nodes in the network and logical adjacent nodes, and performing channel selection. The distributed topological method has advantages of ensuring user network connectivity, eliminating the secondary user interferences and saving channel resource. The distributed topological method can be used for the cognitive AdHoc network.