Plastic pipe caps for protecting steel pipes, featuring a protective plug body that includes a top cap and a flange cap. The flange cap is positioned at the bottom edge of the top cap, with an outer edge cap extending outward from the top cap to the flange cap. A protective plug for steel pipe ends, comprising a protective plug body with a top cap 1 and a flange cap 2. The flange cap 2 is situated at the bottom edge of the top cap 1, with a notched edge 3 on the outer side of the flange cap 2 for easy and quick insertion into the pipe end. An outer edge cap 4 extends outward from the top cap 1 to the flange cap 2 position to prevent the plug from being pushed in too far. A non-slip pad 5 is provided on the outer wall of the flange cap 2 to prevent slipping and falling. Reinforcing ribs 6 are set between the inner walls of the flange cap 2, either in a cross or T-shape, which can be horizontally or vertically placed as needed (cross-shaped reinforcing ribs 6 in Figure 1). The overall structure is simple, easy to manufacture, provides good sealing, and is not prone to falling off during use, thereby extending the service life of stainless steel.