Conclusion of effectiveness evaluation plays an important part for the decision-making of the military operation network (MON). But the existed evaluation risk sources may have an irretrievable effect on the evaluation conclusion. This paper takes MONE evaluation as the background, analyzes the concept of evaluation risk, the necessity of research and the main risk sources in the operation effectiveness evaluation. Focusing on how to reduce the effectiveness evaluation risk, this paper analyzes the major problems in the current research, combining with the meta-evaluation theory, proposes risk reduction mechanism basing on robust management method.