Considering economic operation of the power system with appropriate investment and flexible solution of studied problem with a variety of diverse choices, multi-objective reactive power optimization (MORPO) of distribution system penetrated with distributed generation (DG) is investigated. A multi-objective model for MORPO is constructed and an adaptive multi-objective particle swarm optimization (AMOPSO) algorithm is proposed and applied to nonlinear multi-objective problems with continuous and discrete variables. For demonstrating the feasibility and effectiveness of the proposed model and the application of AMOPSO, simulation results and analysis are carried out with IEEE 33-bus system, which shows the new algorithm can provide multiple solutions for decision makers.