Foldable plastic box

First single convex lugs are arranged at the two ends of a back folding plate of a first plate respectively, first hinge shafts are arranged on the first single convex lugs, a first opening is formedin the middle of the back folding plate, and double convex lugs with second hinge shafts are arranged at the opposite positions of the first opening. The two ends of a forward folding plate of the second plate are provided with a first elastic opening type hinge hole and a first lug groove, the middle of the forward folding plate is provided with a second elastic opening type hinge hole, a pair offirst barbs is further symmetrically arranged at the elastic opening of the second hinge hole, and second lug grooves are formed in the two sides of the second hinge hole respectively. The back folding plate is matched with the front folding plate, the first hinge hole is matched with the first hinge shaft, the second hinge hole is matched with the second hinge shaft, the first single lug is matched with the first lug gro