With the development of information technology, the increase of system information brings new problems to the military system effectiveness evaluation. Aiming at nonlinear, high dimension and strong coupling data of system effectiveness analysis, a data yard based system effectiveness evaluation and decision support method was proposed. Data recovery, subtraction, refinement and reconstruction operations were applied to the simulation data processing, then a data yard cube was built up to meet the multiple demands for system analysis of different levels and data dependency were reduced. Taking task-oriented networked fire control system for example, its system effectiveness evaluation, timeliness evaluation and indices analysis were carried out, and practicability and validity of the method were verified in three levels.Applying data mining technology to the simulation system effectiveness evaluation decision-making,makes it get more extensive application.