The invention relates to a large flange upsetting method for the shaft end of a large-scale wind power main shaft, which includes the following procedures: a forged piece of the wind power main shaftafter initial forging and shaping is hung out from a heating furnace, erected vertically, lifted by a lifting tool and is put in special tool equipment for the large flange upsetting at the shaft endof the wind power main shaft to carry out upsetting the large flange at the shaft end of the wind power main shaft, after the large flange of the shaft end of the wind power main shaft is rotatablelycarried out upsetting to achieve the size meeting technological requirements, the forged piece of the wind power main shaft is vertically hung out from the special tool equipment for upsetting by thelifting tool and is horizontally placed and then is hung into the heating furnace for heating; the next forging process is carried out; the special tool equipment for upsetting consists of two parts of upsetting tool equipment and connecting tool equipment; the upsetting tool equipment includes a upsetting die (9), a gasket component (10), a rotation work table (11), a work table base (13) and a movable work table (14) from top to bottom sequentially; the connecting tool equipment includes a connecting plate (3), an upper anvil stand (4) and an upper anvil (7) from top to bottom sequentially.The method of the invention can shorten forging time, improve working efficiency and reduce forging cost and labor intensity for workers.