Considering the limitation of single index evaluation, we made evaluation to directed graph of C4ISR structure based on four indexes of intelligence efficiency, dexterity, connectivity rate and command-control efficiency. The method of optimal combined weights was adopted to reflect the subjective judgment of decision maker and objective observation information. Weighted product model was adopted to reflect the feature that any of the index decreases may lead to decreased system structure effectiveness being unable to rise again. Matlab was used for calculation of the assessment case, and the result verified the rationality and effectiveness of the evaluation method.directed graph; optimal combined weights; weighted