Abstract: By improving the formula for solving the approaching degree,a method for evaluating the effectiveness of weapon systems according to the grey target principle is established.The grey target theory is used to set up the model for mathematical evaluation;the tactical and technical performance indices,which reflect the effectiveness of weapon systems best,is used to form the index series of weapon systems to be evaluated(namely,the modes),and the standard mode of these index series is derived according to the grey target theory,thereby evaluating the effectiveness of weapon systems as can be evaluated by solving the degrees of approach of each mode to the standard one.In the case in evaluating the effectiveness of rifles AK74,AK47 and M98K,the approaching degrees of AK74,AK47 and M98K are respectively 0.983 7,0.737 3 and 0.643 9.The fire assault indices of AK74,AK47,and M98K,which reflect the effectiveness of rifles,as solved by the conventional method,are respectively 2.52,2.25 and 1.00.Regarding the effectiveness,this method gives the same conclusions as the conventional one and the actual performance of three weapons in battlefields: AK74 is the best,AK47 the second,and M98K the third.The method is improved in meeting both objectivity and maneuverability simultaneously,for its calculating process is mostly of simple algebraic operation,and need not to deal with those subjective factors based on score-giving by experts in many of the conventional methods.