The invention discloses a client-service-oriented multinational game strategic decision simulation and deduction high level architecture (HLA) simulation system which can overcome defects of poor generality, low stability and complex operation in the prior art. All components of the system are connected into a local area network built with the HLA and a run-time infrastructure (RTI) soft bus as support technology; a plot generation module generates plots needed by the whole situation deduction; a practice management module manages and controls the deduction process, states of al parties and decision schemes according to the plots or instructions coming from a client of the director party; in each game, a client of the game playing party extracts a basic decision opinion collection from a decision scheme base through an official document editing module and sends decision opinions selected from the basic decision opinion collection and a self drawn action plan to the decision scheme base; and a simulation and deduction module performs deduction for the decision schemes collected in the decision scheme base to form a situation to be displayed in a comprehensive situation module.