Traditional task solution schemes in Wireless Sensor Networks (WSNs) are mainly not suitable for complicated task processing due to high energy consumption and long processing delay. In this paper, we proposed an energy efficient Complicated Task Solution scheme for real-time task processing based on node Cooperation (CTSC), which consists of two main phases: task grouping and task allocation. In the task grouping phase, complicated tasks are divided into different groups based on task graph. In the task allocation phase, based on node cooperation, different group tasks are allocated to different nodes by using bid invitation. Thus, multiple tasks can be processed in parallel, which ultimately reduces task processing delay and limits communication overheads. Simulation results show that CTSC is much more suitable for large scale WSNs. In addition, CTSC outperforms related works in terms of shorter response time of task processing and less energy consumption.