The purpose of this study is to show the causal relations between user-oriented performance indicators for the logistics support management and then to determine the rate to improve Logistics Support Performance by increasing Accurate Demand Estimate Degree(ADED). A system dynamics model is built, which well explains the dynamic characteristics of logistics support. Its validity is checked by the model structure test and the model behavior test of Vensim Professional 5.8a. The results of simulation analysis with 4 scenarios confirm a mechanism that the increment of ADED with the shortening of logistics support periods leads to the improvement of logistics support performance. It uses the sample data of repair spare parts of K1 Tank from 2005 to 2008.