In dynamic distributed computing environment, due to the uncertainty of resource and computation execution time, how to effectively solve the scheduling problem of interdependent tasks consisting of complex computations has become a significant research topic. As a heuristic just-in-time scheduling algorithm, the priority-based level (PBL) has been proved to have better performance than other existing algorithms. However, due to its own limitations, PBL will cause excessive computing overhead when dealing with high parallelism of ready tasks. To overcome this problem, we propose an improved priority-based level (iPBL) algorithm. Experiments show that iPBL can significantly improve the executing efficiency of PBL algorithm and maintain the same scheduling results as PBL.