To improve the performance of LNG cold energy power generation systems, scholars have made great efforts to enhance the cycle configuration and select the suitable working fluid. In this process, the improvement of the configuration and the selection of the working fluid are mostly independent, so that the possibility of missing the optimal combination is great. To solve the problem, the superstructures of the two-stage condensation Rankine cycle (2C-ORC) and the three-stage condensation Rankine cycle (3C-ORC) are established in this work, which contain different compression and expansion layouts. The selection coefficients of the working fluids are also introduced at the same time, which can optimize the compositions of mixed working fluids. In this way, the system configuration improvement and working fluid selection can be realized simultaneously. In this work, the net power output and the total cost are taken as the objective functions for the single-objective optimization, respectively. The optimal c...