The invention provides a door frame of a fan tower, a door frame unit, a production method of the door frame and the fan tower, wherein the door frame of the fan tower comprises an upper circular arc section, a lower circular arc section, and two straight line sections positioned at the sides; and a welding line of the door frame is positioned on the upper circular arc section and the lower circular arc section. The position of the welding line of the door frame is changed, and the welding line of the door frame is arranged in an area with lower stress, so that the stress concentration in the welding line is reduced, and the fatigue bearing capacity of the door frame is improved; the door frame structure is changed, so that the stress concentration between the door frame and a tower cylinder wall is reduced, the bearing capacity of the tower cylinder wall is improved, and the tower failure caused by excessive stress in the welding line is reduced; and under the condition of equal load, the weight of the tower is reduced, and the cost is reduced.