The invention relates to the technical field of power network planning, and specifically relates to an online assessment system for the feasibility study of a high-voltage distribution network project. The online assessment system comprises a core service module, a preliminary plan release module, a subordinate department notification reception reminding module, a subordinate department feasibility study material uploading module, a feasibility study material automatic checking function, a superior department feasibility study material reception reminding module, a feasibility study material assessment module, a subordinate department assessment opinion checking and accepting module, a subordinate department uploading condition statistics module and the like, and completes the work flow of the entire feasibility study process. The invention further provides an online assessment method for the feasibility study of the project. Notifications, reporting and assessment occurred offline are informationized into the system, the preliminary planning and reporting work are enabled to be in order, a lot of repetitive work is reduced, the whole assessment period is shortened, and the work efficiency of assessment is improved.