Abstract: Distributed energy resources are small-scale and widely-distributed, which make them unable to directly participate in the energy trading. Therefore, it is proposed by an optimal energy trading strategy for local electricity market with multiple distributed energy resource (DER) aggregators. Firstly, scattered DERs are formulated as aggregators to participate in the energy trading of the local electricity market, and distribution system operators participate act as system owners to participate the energy trading of the local electricity market and the wholesale market of the upper grid. Secondly, a two-tier model of optimal energy trading in local electricity market with multiple DER aggregators is established. Finally, the Karush-Kuhn-Tucker (KKT) condition, the strong duality theory and the big-M method are adopted to transform the proposed model into a single layer model. The simulation results show that the proposed model can effectively promote DER to participate in energy trading and improve the operation efficiency of the overall power system.