The invention provides a cuckoo search algorithm based satellite-land cognitive system frequency spectrum access method and relates to a frequency spectrum access method. The invention aims to solve a problem of low search speed of a prior access method. According to the invention, based on a satellite-land share frequency spectrum network structure, available frequency spectrum resource is divided into a plurality of sub channels. A cognitive user performs quick search on unoccupied sub frequency bands through an improved cuckoo search algorithm and achieves dynamic frequency hopping to the unoccupied frequency bands for secondary utilization. Besides, by combining with a step length control amount alpha fitting the cuckoo search algorithm dynamically and the probability Pa that a cuckoo bird egg is found by a host bird, the unoccupied frequency band capturing possibility is increased, and excess search can be reduced and search speed can be increased truly. At the same time, the algorithm is prevented from falling into local optimal solution and improvement of algorithm convergence speed is ensured. The method provided by the invention is suitable for frequency spectrum access process in communication field.