The sensitivity analysis of a polygeneration energy system fueled with duo fuel of coke oven gas and coal gas is performed in the study, and the focus is put on the relations among syngas composition, conversation rate and performance. The impacts of the system configuration together with the fuel composition on the performance are investigated and discussed from the point of cascading utilization of fuel chemical energy. First, the main parameters affecting the performance are derived along with the analysis of the system configuration and the syngas composition. After the performance is being simulated by means of the Aspen Plus process simulator of version 11.1, the variation of the performance due to the composition of syngas and the conversion rate of chemical subsystem is obtained and discussed. It is obtained from the result that the proper conversion rate of the chemical subsystem according to the specific syngas composition results in better performance. And the syngas composition affects the optimal conversion rate of the chemical subsystem, the optimal point of which is around the stoichiometric composition for methanol production (CO/H = 0.5). In all, the polygeneration system fueled with coke oven gas and coal gas, which can realize the reasonable conversion of syngas to power and chemical product according to the syngas composition, is a promising method for coal energy conversion and utilization.