The invention provides an optimal planning method and device for the power transmission capacity of a new energy base delivery channel. The method comprises the following steps that: carrying out newenergy base output data statistics; according to the new energy base output data, constructing a power grid time sequence simulation model; and according to the power grid time sequence simulation model, carrying out the optimal calculation of the capacity of the new energy base delivery channel to obtain the optimal value of the capacity of the delivery channel. By use of the technical scheme provided by the invention, the wind power and solar power generation output characteristics of the new energy base and the consumption ability of a new energy receiving end power grid are considered, andtherefore, a calculation result is accurate and reliable. A quantitative relationship between the power transmission capacity of the new energy delivery channel and a new energy limitation level is established, and the required power transmission capacity of the delivery channel can be selected according to practical operation requirements.