Plastic pipe caps for protecting steel pipes, featuring a protective plug body that includes a top cap and a skirt cap. The skirt cap is positioned at the bottom edge of the top cap, with an outer skirt cap extending outward from the perimeter of the top cap. A protective plug for steel pipe ends, comprising a protective plug body with a top cap 1 and a skirt cap 2. The skirt cap 2 is located at the bottom edge of the top cap 1, and an indentation 3 is provided on the outer side of the skirt cap 2 for easy and quick insertion into the pipe opening. An outer skirt cap 4 extends outward from the perimeter of the top cap 1 to the skirt cap 2 position, preventing the plug from being inserted too deeply. A non-slip pad 5 is attached to the outer wall of the skirt cap 2 to prevent sliding off, and reinforcing ribs 6 are set between the inner walls of the skirt cap 2, shaped in a cross or T-form. These ribs can be either horizontally or vertically placed as needed (cross-shaped reinforcing ribs 6 are shown 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 pipes.