—This study is aimed at investigating the effects of cut-off ratio on the endoreversible Dual cycle performance with considerations of heat transfer loss and specific heat ratio. By using finite time thermodynamics theory, the relations between the net work output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between net work output and the thermal efficiency of the cycle, are derived. The results shows that if compression ratio is less than certain value, the net work output first decreases and then starts to increase as the cut-off ratio increases. While if compression ratio exceeds certain value, the increase of cut-off ratio make the net work output bigger. The results also shows that the maximum net work output and the optimal thermal efficiency corresponding to maximum net work output first increase and then start to decline as the cut-off ratio increases. The thermal efficiency and the working range of the cycle decrease when the cut-off ratio increased. The results obtained in this work can help us to understand how the cycle performance is influenced by the variation of the cut-off ratio, and they should be considered in practical cycle analysis.