The invention proposes a caching method based on self-organized cooperation of small base stations in an ultra-dense network, belonging to the technical field of wireless communication. Including: firstly, according to the load capacity and location of small base stations in the ultra-dense network, the similarity matrix of small base stations is obtained; then, according to the similarity matrix and the number k of small base stations in each cluster, clustering is carried out, and the load capacity is selected A good small base station acts as a cluster head; cache files in the small base station and macro base station according to the file caching strategy; after the user accesses the base station, request to obtain the file; finally, judge whether the value of k exceeds the maximum value K set in the cluster , if so, output the k value that minimizes the user's average download delay; otherwise, continue to update the k value and continue to re-cluster. The present invention allocates resources in a cluster through the idea of self-organization, utilizes mutual cooperation and self-organization among small base stations, effectively improves the cache hit rate, reduces user download time delay, and satisfies various service requirements.