The paper proposes a reactive power optimization method of distribution network based on Case-Based Reasoning from the perspective of data analysis. First, historical cases are selected based on the symbolic features of the cases. Second, cases selected will be screened by some thresholds. In order to reduce the time of calculating the similar degrees, the principal component analysis is conducted to reduce the dimensionality of the original features, and the entropy weight method is used to determine the weight according to the amount of information contained in each feature. Third, the similar degrees between the screened historical cases and the current case are calculated, and the optimal control scheme suitable for the current case is selected according to the similar degrees. The simulation study shows that the optimization results and the computation time of the proposed method proposed are superior to those of the conventional algorithms.