The invention discloses a semi-automatic box folding machine of a semi-packed box of a heat collector. The semi-automatic box folding machine comprises a base, a box folding machine body, an upper die, a lower die and margin driving devices, wherein the box folding machine body is formed by a left bracket and a right bracket and is vertically arranged on the base, a cross beam is connected between the left bracket and the right bracket, a feed plate and a discharge plate are respectively installed on the cross beam, the feed plate and the discharge plate are positioned on the same plane and are separated to form a die cavity, the upper die can descend, so that a flat box plate is placed on the feed plate and the discharge plate is pressed into the die cavity until the box plate makes contact with the lower die, and then paper box folding is performed through the margin driving devices positioned on both sides of the box folding machine body, so as to complete automatic box folding. Manual operation is replaced, so that the labor cost is reduced, the labor intensity of workers is greatly reduced, the semi-automatic box folding machine can be easily kept in an efficient working condition for a long time, and the quality stability is guaranteed. In addition, the capacity and the working efficiency are greatly improved, thereby effectively increasing production profits.