The invention discloses an automatic box filling machine for small fruits. The automatic box filling machine comprises a horizontally-placed belt conveying mechanism, a feeding area, a box filling mechanism, a discharging area and a controller, wherein the horizontally-placed belt conveying mechanism, the box filling mechanism and the discharging area are arranged in sequence in the conveying direction of the belt conveying mechanism, and the controller is used for controlling the mechanism to work; the box filling mechanism comprises a supporting frame, a fruit stacking funnel, a placing mechanical arm and a hose, wherein the supporting frame is vertically arranged at the upper end of the belt conveying mechanism, the fruit stacking funnel is arranged above the supporting frame, the placing mechanical arm is arranged below the fruit stacking funnel, one end of the hose is connected with the lower end of the funnel, and the other end of the hose is connected with the placing mechanicalarm. According to the automatic box filling machine, a paper box can be continuously conveyed into the box loading mechanism from the feeding area through the belt conveying mechanism, the box can beinstalled, the paper box filled with fruits is conveyed to the discharging area for manual sealing, and the working efficiency is greatly improved; and the placing mechanical arm is an X-Y-Z-axis mechanical arm, and can be used for carrying out S-shaped box filling on the fruits layer by layer, the collision damage of the fruits in the box filling process is reduced, the structure is simple, andthe use is convenient.