The tasks scheduling model is established based on multi-factors that include communication abilities between any two sites, process ability of the site and the reliability of site in complex and dynamic environment. The Target heuristic function is constructed combined minimum executing time and reliability of site. Simulation result demonstrates the factors concern with task scheduling model accord actual situations and its can be satisfied task scheduling demand in complex grid environment. It can be found optimization value of the local target heuristic function combined minimum executing time and reliability of site.