Task scheduling is one of the core contents in distributed computing system study area. The task scheduling model based on dynamic trust has been confirmed to have good performance in volunteer computing and grid computing systems, which can deal well with the uncertainty of the node. This paper firstly introduces the general situation of the existing task scheduling model based on dynamic trust, and analyzes the shortages of the model, such as task size, deadline and computing power of the redundancy group. Then a new task scheduling model is proposed, which can be used in independent tasks calculation of BOINC. The new algorithm optimizes the definition of reliability and takes the size and deadline of task and the calculation capability of the redundant group into account, which improves the calculation throughput and reduces the computation time.