The invention provides a power transmission and distribution network coordination planning method considering equivalent optimization of a power distribution network, and belongs to the field of powersystem planning. According to the method, layered planning is carried out on the power transmission and distribution network; a power distribution network planning model is established for each powertransmission network node comprising the power distribution network, and the power distribution network net income corresponding to the total number of the different power distribution network itemsand the corresponding new power distribution network loads are obtained through optimization calculation to serve as boundary parameters of the power transmission network model. In the power transmission network model, the operation constraints of the power transmission network are established based on a direct current power flow equation; the specific power distribution network investment schemeis optimized and selected according to the planning result of the power distribution network under the constraint that the power distribution network and the fixed power transmission network total investment amount, and the expansion scheme of the power transmission network is determined. According to the method, layered planning is carried out on the power transmission and distribution network, the calculation efficiency is improved, an effective transmission and distribution coordination planning scheme can be obtained, and the method has high application value.