In wireless cognitive radio networks (CRNs), user will send the sensing data to neighbors for spectrum allocation. Actually only part of data will affect the allocation result. The transmission of unused sensing data isn’t cost-efficient because it consumes a great deal of computing and network resource, especially for CRNs in which the spectrum and power resource is very precious. We propose an improving transmission availability algorithm— SkyChannel Query, which can find the non dominated channels and only transmit information of these channels. The experimental results show the advantages of our algorithm in terms of saving computing resource and improving transmission availability.