The economic operation of the microgrid is a multi-objective and multi-constraint problem. In order to distinguish the importance of each objective, this paper proposes a centralized control model. The operator uses the dualistic contrast to sort the importance of the generation cost in generation-side, electricity cost in demand-side and reliability cost, and uses the relations among tone operator, fuzzy scale and membership degree of relative importance to determine the weighted coefficient, and the multi-objective problem is transformed into the single objective problem. The operator uses improved particle swarm to deal with the generation cost in generation-side, electricity cost in demand-side and reliability cost. Comparative analysis of different performance index is made, and the example simulation shows that the proposed model is effective to schedule the output power of distributed generation and load, which ensures both the economic operation and the reliability of the microgrid. This work is supported by National Natural Science Foundation of China (No. 61673174).