The invention discloses a mounting method of a basic transition section of a marine fan. The method comprises the following steps of preparation of limiting devices and embedded reinforcing bars, construction of permanent cushion blocks, arrangement of assistant cushion blocks, hoisting of a transition section, the fine adjustment of the transition section in a horizontal direction and in a vertical direction, and the completion of the butting of the final transition section and the permanent cushion blocks which are arranged in advanced. Through the adoption of the method disclosed by the invention, the collision between a flange and an anchor bolt of the transition section can be avoided, besides, the accurate connection between the transition section and an embedded anchor bolt can be guaranteed, the mounting is convenient, the mounting efficiency is high, and the work safety is high.