In this paper, we design a fine-grained task execution scheme under the cooperation of terminals, edge and cloud servers. Firstly, we build a virtual hierarchical architecture for terminal-edge-cloud cooperative network and introduce SDN technology to balance the edge load and achieve efficient network information management. Then our task execution scheme is proposed with two task serving patterns and three execution mechanisms, specifically, for tasks with pattern of “served as a whole”, we build an optimization problem to minimize delay and energy consumption jointly; for tasks with pattern of “served with segmentations”, a Subtask Scheduling Parallelism Maximization (SSPM) algorithm based on dynamic list scheduling is designed to maximize the parallelism degree of subtasks execution as much as possible. Finally, we carry out our simulation on NS-3 platform.