Abstract: With the changing of global security situation, the focus of global security has gradually shifted to "traditional threats", and military operations have also gradually been expanded to carry out multi-military tasks. U.S. Army has studied assistant decision making problems about multi-military tasks and does a lot of works about modeling and simulation. In this paper, the tools and systems of assistant decision making about multi-military tasks are outlined, then the capability of Joint Analysis System (JAS) and Joint Theater Level Simulation (JTLS) is especially discussed. The technology trend of modeling and simulation related to multi-military tasks is analyzed, and some inspirations and suggestions are proposed, combined with the current research and construction situation in the field of multi-military tasks.