The invention discloses a cellular downlink network energy efficiency optimization system and method based on a cache popular content; contents with different popularity are cached in a base station by adopting a distributed cache method; and the cellular network is divided into SGW, BS and UE, wherein the SGW caches a file requested by the BS, and each BS is provided with a cache device capable of caching Nc contents and is connected with the SGW through a backhaul link with the capacity of CBH; when the file requested by the user is cached in the local base station, the base station directlyacquires the file and transmits the file to a user; otherwise, the file is acquired from the SGW and transmitted to the user through the backhaul link. A popular content is a content that is more frequently requested by the user within a time T0, and the downlink energy efficiency gain is the ratio of the number of bits transmitted in the whole downlink network and the consumed power. The distributed cache is that four adjacent base stations cache different contents, and when each user requests the content, a nearest base station for caching the content is selected; the method reduces the redundancy of the base station content and increases the cache hit rate at the same time.