Abstract: In order to further reduce the carbon emissions of a park-level integrated energy system (PIES) and optimize the flexibility of the combined heat and power (CHP) unit output, a PIES low-carbon economic dispatch strategy considering the improvement of the ladder-type carbon trading and the flexible thermoelectric output of the CHP is proposed. Firstly, combining the genetic algorithm with the fuzzy control, a genetic fuzzy carbon trading parameter optimizer is designed to improve the existing ladder-type carbon trading mechanism and realize the adaptive change of the mechanism parameters. Secondly, a Kalina cycle and an electric boiler (EB) are added to the traditional CHP to construct the CHP thermoelectric flexible output model to meet the different needs of the electric and the thermal loads simultaneously. Then, a flexible index model, namely the ratio of the electric and thermal output, is proposed, and the ratio range of the electricity and heat output is calculated to measure the flexibility operation of the CHP. Finally, the improved ladder-type carbon trading mechanism and the thermoelectric flexible output model of the CHP are synergistically optimized. The PIES low-carbon economic optimization model is established with the goal of minimizing the sum of the system operation cost and the carbon trading cost. Case analysis shows that the proposed strategy is able to effectively reduce the economic cost and the carbon emissions, and also expand the flexible output adjustment range of the CHP, providing a reference for the low-carbon economic dispatch of the PIES.