This paper describes a novel gas turbine and cascade CO2 combined cycle which composes of a gas turbine, a supercritical CO2 Brayton cycle and a transcritical CO2 cycle. To show its thermodynamic potential, a new solving pro(c)edure for performance evaluation and optimization of this combined cycle was proposed. Genetic algorithm (GA) was introduced for parameter optimization in order to get better combined cycle performance. Simulation results showed that the GT-cascade CO2 combined cycle did have better thermodynamic performance than conventional GT-steam Rankine combined cycles. And this GT-cascade CO2 combined cycle could have an efficiency increase of more than 17.03% from singe gas turbine cycles. Moreover, this combined configuration could be applied to gas turbines of different power levels. Through GA optimization, the thermal efficiency could achieve 52.53% for the Taurus 60 GT-cascade CO2 combined cycle. Sensitivity simulation results indicated that the proposed cascade CO2 cycle was favorable to counteract the influence of ambient temperature on the combined cycle performance. (C) 2017 Elsevier Ltd. All rights reserved.