The invention relates to a gradual speed reducing device, particularly to a gradual speed reducing control box with an oil magnetic drum, which is used for autozoom glasses and the like in ophthalmonogy. The invention aims to provide a gradual speed reducing control box with an oil magnetic drum comprising a box body, adjustment devices located at both sides of the box body, and a power gear, wherein the box body is internally provided with a power device for providing rotational power; the box body comprises a front cover and a back cover; the power device comprises a spring button, a directional wheel, a spring coil and a spring gear; the box body is also internally provided with a speed reducing device for reducing the rotational speed of the power device and a speed limiting device for limiting the rotational speed of the power device, wherein the power output part of the speed reducing device is connected with the power gear through an engaging and disengaging device; the speed limiting device is an oil magnetic drum, and the speed reducing device is a speed reducing gear set, wherein an input gear of the gear set is engaged with the spring gear, and an output gear of the gear set is engaged with the oil magnetic drum.