The invention relates to a reactive optimization method and system of a distribution network. The method comprises: a high-dimensional random matrix is established based on a distribution network and a covariance matrix of the high-dimensional random matrix is calculated; a spectral distribution circular ring is constructed based on the covariance matrix and a to-be-measured matrix in the spectral distribution circular ring is determined; and on the basis of the to-be-measured matrix, a reactive power compensation point and a reactive power compensation capacity of the distribution network are determined. Because of introduction of the high-dimensional random matrix theory into the reactive power compensation analysis of the distribution network, a novel analysis method is provided for reactive power compensation of the distribution network.