The invention relates to a system simulation method based on quantum mechanics description. The method comprises the following steps: defining a simulation model, performing time advancing calculation on the simulation model, and updating the state of the simulation model. A simulation description basis is redefined according to the quantum mechanics thought, and a basic calculation module reading rule of the simulation model is planned, so that a simulation method which supports QSS acceleration and multi-branch forecasting simulation is formed, and parallel operation of time sequence simulation is realized; multi-branch simulation analysis can be carried out by applying the parallel space-time theory, and a plurality of branches are established in a simulation process to comprehensively analyze various possibilities; and the simulation method has the capacity of multi-branch simulation and can simulate the effects of different decision results and random events at any moment serving as a start point.