A system for implementing a Content Distribution Network, CDN, based on a Software Defined Network, SDN, comprising: an application unit, orchestration unit, control unit and data forwarding unit in the SDN, wherein the application unit comprises: a requesting module and an operation module, wherein the requesting module is configured to add a complete service logic function of the CDN, and when receiving a CDN application request, send a resource requirement request and a service orchestration request to the orchestration unit; the operation module is configured to, after receiving information indicating completion of a reservation request, execute a related operation according to a content distribution request or a media access request; wherein, the related operation comprises: content distribution, content caching, content routing and content delivery corresponding to the content distribution request or the media access request; the orchestration unit comprises: a resource cooperation module and an orchestration feedback module, wherein the resource cooperation module is configured to receive the resource requirement request and the service orchestration request, perform service orchestration in combination with related information of the SDN, and send the reservation request for a required resource to the control unit according to the service orchestration; wherein, the related information of the SDN includes: network topology information, network load balancing information, network routing information and firewall deployment information of the SDN; the orchestration feedback module is configured to, after the reservation request for the required resource is completed, feed the information indicating completion of the reservation request for the required resource back to the application unit; the control unit is configured to allocate the resource required by a CDN application according to the reservation request, determine content distribution and content delivery paths in combination with a network load balancing and routing condition; after the allocated resource required by the CDN application is obtained, create a data link Layer L2 and network Layer L3 forwarding table according to a related forwarding policy of an SDN control plane, transmit the data link Layer L2 and network Layer L3 forwarding table to the data forwarding unit, and feed completion of the reservation request for the required resource back to the orchestration unit; wherein, the related forwarding policy includes: a hotspot distribution policy, a load balancing policy and a content routing policy; and the data forwarding unit comprises related network equipment for SDN data forwarding, and is configured to store related data of the CDN application according to the allocated resource required by the CDN application, and perform data forwarding according to the L2 and L3 forwarding table determined by the control unit when the application unit executes the related operation; wherein, the related network equipment for the SDN data forwarding comprises: an OPENFLOW switch, OPENFLOW router, OPENFLOW gateway, OPENFLOW storage server and OPENFLOW custom equipment for SDN data forwarding.