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 placement into the pipe opening. An outer edge cap 4 extends outward from the top cap 1 to the flange cap 2, preventing the protective plug from being inserted too deeply. A non-slip pad 5 is provided on the outer wall of the flange cap 2, preventing it from falling off. Reinforcement ribs 6 are set between the inner walls of the flange cap 2, in a cross or T-shape (as shown in Figure 1, the cross-shaped reinforcement ribs 6 are placed vertically), making the overall structure simple, easy to produce, and providing good sealing effects. The product is not easily dislodged during use, thereby extending the service life of stainless steel pipes.