Grid connects distributed resource into a mass environment for computing.The scheduling algorithm has much influence over the efficiency and performance of grid.EASY-backfill is a classical scheduling algorithm with simple program,little computation workload and relatively high performance.But the algorithm is based on assumptions that all resources in the grid are absolutely stable,and the performance forecast of jobs is accurate and reliable.Yet these conditions are ideal and unpractical.In this paper,we use some unstable parameters to build a different model of unstable grid resources,and modify the EASY-backfill algorithm according to the model.We make effort to keep the performance and effectiveness of the algorithm on condition that the modified algorithm sensitive to the unstable and unpredictable grid resource.We also make comparison between the classical and modified algorithm and do some discussion on the influence of different unstable parameters.