As the globe faces major difficulties such as climate change, environmental pollution, and limited energy resources, improving energy efficiency and decreasing the environmental effects of energy systems have become research priorities. A novel mass integration cogeneration system (MICHP) is proposed in this paper. In addition, a mathematical model relating the basic physical properties of the working fluid to the system's performance has been developed. R1233zd(E), R1224yd(Z), R601a, R245fa, and acetone have been chosen to be applied to the MICHP to confirm the model's accuracy. By utilizing the technique for order preference by similarity to an ideal solution, the entropy weight method, and energy, exergy, economic, and environmental analyses of the MICHP, the general efficiency of the working fluid is further explored. The results show that the intermediate heat exchanger is the largest exergy destruction equipment in the system. R601a has the highest return on investment of 0.53, and the annual operating cost is found to be proportional to the latent heat of the working fluid. R1233zd(E) has the lowest environmental impact, with a total equivalent warming impact of -4.89×106 kgCO2eq. The multi-criteria decision analysis of the working fluid agrees with the order of the proposed mathematical model's results, proving the model's accuracy. Consequently, the mathematical model can provide a helpful technique guide for working fluid selection in cogeneration systems.