Abstract: Transmission section limit（TSL） is an important boundary condition for the safe and reliable operation of power grid. As the scale of the power grid expands, the operation mode of the interconnected power grids is more and more complicated and variable, and many TSLs are only applicable under such conditions as certain unit start-up mode or related branch power flow level, and even these conditional transmission sections are interrelated. The traditional determination of the onset condition based on human experience requires repeated attempts of TSLs to optimize the power generation plan, which makes the optimization and decision-making process of power generation plan very complicated. Based on the traditional optimization model of power generation plan that considers fixed TSLs, and aiming at the characteristics of the conditional transmission section limits（C-TSLs）determined by the intervals which the relevant variables belong to, this paper proposes an optimization modeling technique by integrating power generation plans and C-TSLs. This model can achieve the automatic matching of C-TSL and power generation plan, and further tap the transmission potential of the power grid while ensuring the safety of the power grid. Finally, based on the proposed model, an example analysis is made on typical C-TSL scenarios such as cross section power flow ranges and the number of running and shut down units to verify the effectiveness of the model.