Aimed at the resource scheduling problem of phased array radar in multiple target tracking, this paper proposes a task scheduling algorithm based on modified priority. The algorithm introduces the threat of the target to radar into the design of the target task priority. Firstly, the target threat degree is defined. A method that combines comprehensive decision-making of information entropy with subjective weighting is used to calculate the target threat degree in accordance with various parameters of the target and radar. And then, the algorithm synthesizes planning of the target threat degree, the priority of function mode of the task and the deadline of the task to obtain the comprehensive priority. Finally, the calculation process of target threat degree and task scheduling are simulated. The simulation results indicate that the calculation results of target threat degree conform to the demand for tracking resource distribution in different target threat degrees of targets, and the algorithm has a certain superiority for executing high threat tasks, compared with the traditional algorithm.