Plastic pipe caps for protecting steel pipes, featuring a protective plug body which 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, and has a notched edge 3 on its outer side for easy and quick insertion into the pipe opening. An outer edge cap 4 extends outward from the top cap 1 to the flange cap 2, preventing the plug from being inserted too deeply. A non-slip pad 5 is provided on the outer wall of the flange cap 2 to prevent it from falling off. Reinforcing ribs 6 are set between the inner walls of the flange cap 2, either in a cross or T-shape (as shown in Figure 1, the cross-shaped reinforcing ribs 6 are placed vertically), offering a simple structure that is easy to produce and provides good sealing effect, making it less likely to fall off during use and extending the service life of the stainless steel.