The invention relates to an additive manufacturing technology and particularly discloses a control device for power distribution quantity during additive manufacturing. The control device is arranged in a forming chamber, a powder receiving box is arranged in the forming chamber, a weight detection device is arranged on the powder receiving box, and a powder paving platform is arranged below the powder receiving box. The control device comprises at least two pairs of light producing devices and light intensity sensing devices, which are arranged below at least one end of the powder paving platform, residual powder falls off from the end part of the powder paving platform, and the falling trajectory is positioned between the light producing devices and the light intensity sensing devices. The weight detection device, the light producing devices and the light intensity sensing devices are all connected to a controller. Through arranging the light producing devices and the light intensity sensing devices, the margin of falling powder can be detected. Through comparing the powder margin value with a preset range by the controller, the total quantity of distributed powder is adjusted according to the comparison result, and after multiple times of adjustment, the optimal powder distribution quantity is determined. The integrity of a paved powder layer can be ensured, and powder consumption is reduced as much as possible.