The present disclosure relates to a partition method and a partition device for a power system and belongs to a field of an evaluation and control of a power system. The method includes steps of: obtaining a quasi-steady sensitivity matrix according to generators participating in automatic voltage control and load buses in the power system; obtaining a power system model according to the quasi-steady sensitivity matrix and the load buses; determining principal component vectors and principal component singular values according to the power system model; determining a principal component vector dominated by each generator according to the principal component vectors and the principal component singular values; and partitioning the generators dominating a same principal component vector to a partition, and partitioning the load buses according to a partition result for the generators.