The invention relates to a tri-network integration application terminal accessing device based on cloud computing and a realization method. The accessing device is realized in a way of embedded software and hardware integration, and comprises a cloud accessing unit and a cloud processing unit. The cloud accessing unit and the cloud processing unit are used for adapting a cloud-computing based tri-network integration system integrating a virtual Internet, a virtual telecommunication system and a virtual broadcast and radio network and performing cloud application operation. The cloud accessing unit and the cloud processing unit are connected with a main control unit of a terminal system. An adaption port is arranged for obtaining tri-network integration services on a cloud service end. Via the cloud accessing unit, self-adaption of a tri-network integration heterogeneous network environment and automatic distinguishing for cloud application modes can be achieved. The cloud processing unit obtains related information of the cloud accessing unit, performs cloud application operation, and distributes corresponding access resources and cloud service resources to the terminal system. According to the invention, node resources of a cloud server can be fully used; problems like multi-network parallel access and cloud application adaption in tri-network integration can be effectively solved; and low-cost and flexible deployment of the terminal is achieved.