The invention belongs to the technical field of power system scheduling automation and relates to a multi-unit coordinated scheduling method considering transmission section capacity constraints. Themethod includes the following steps that: with maximizing generated power under the constraint of the TTC (Total Transfer Capability) of a power transmission cross section adopted as an objective, a cascade hydropower station coordinated optimal scheduling model is established, a transmission section transfer capability-constrained large and medium-sized hydropower station operation constraints are introduced on the basis of a complex overflow hydropower station model; and a water-to-power conversion relationship and a water level-capacity relationship are linearized, and nonlinear constraintsin the model are transformed into linear constraints, an INLP (integral non-linear planning) problem-based original model is converted to an ILP ((integral linear planning) model, and calculation results are outputted. According to the method of the invention, the constraints of power transmission capacity on hydropower absorption are fully considered, and large and medium-sized hydropower stations are utilized to adjust water storage capacity, so that a hydropower absorption rate can be effectively increased; and benefits from the compensation of small hydropower stations by large hydropowerstations during a dry period can be increased, and therefore, total generated power can be increased. The method can be used for the formulation of cascade hydropower station power generation plans and provide guidance for the benefit analysis of power transmission line expansion.