The invention discloses an adjusting tool for assembling a fan cabin cover. The adjusting tool comprises a top-set device, an L-shaped top plate and a movable trolley, wherein the top-set device is connected to the L-shaped top plate; an adjusting device for adjusting the horizontal movement of the fan cabin cover is arranged at the upper part of the top-set device, while a trolley guide rail is arranged at the bottom of the of the top-set device; the movable trolley is matched with the trolley guide rail, and comprises a support; a jack is arranged on the support and an iron wheel is arranged at the lower part of the support; a groove is formed at the outer circle at the axial middle part of the iron wheel; a projection is arranged in the middle part of the trolley guide rail; the guide rail projection is matched with the groove of the iron wheel in position; the adjusting device comprises a lead screw and a nut; the nut is arranged at the upper end of the top-set device; and one end of the lead screw is connected to the L-shaped top plate. The adjusting tool is simple in structure, convenient to operate, safe and reliable, and high in efficiency.