Aiming at the phenomenon of “degeneration” of Bootstrap regenerated sub-samples under the condition of extremely small sub-samples,it is proposed to use prior information such as the test information of similar type of missile as a sample of Bootstrap method.It is pointed out that when using the prior information,the compatibility with field experimental information should be taken into consideration,and the consistency of the prior information from different sources should also be checked.A method for pre-processing the prior information to evaluate missile hit accuracy is proposed.Then,in order to avoid the introduction of too much prior information and “overwhelming” the field experimental information,an improved weight distribution scheme is proposed based on the importance sampling idea,and an improved Bootstrap method is obtained.Finally,combined with the missile hit accuracy evaluation example,the pre-processing of the prior information is completed.The simulation proves that the improved Bootstrap method can improve the point estimation and interval estimation of the landing point density,and enhance the credibility of the hit accuracy assessment.