In this paper, the influence of distributed energy on the harmonic of active distribution network is studied. Firstly, the distributed energy in active distribution network is classified according to the type of harmonic source, which includes current type and voltage type harmonic source. Then harmonic current’s generation, propagation and superposition rules are analysed by simulation method, as the harmonic source’s power, the load at connected point and connected point change. The generation and propagation of harmonic voltage in ADN are studied, considering the power and connected point of the harmonic source’ change. As the simulation results, the conclusions are drawn to guide the connected points’ selection of the units in ADN.