Plastic pipe caps for protecting steel pipes, featuring a protective plug body with a top cap and a skirt cap, the skirt cap located at the bottom edge of the top cap. The top cap extends outward to the skirt cap with an outer skirt cap. A protective plug for steel pipe ends includes the plug body, with a top cap 1 and a skirt cap 2. The skirt cap 2 is positioned at the bottom edge of the top cap 1, with a notched edge 3 on the outer side for easy and quick placement into the pipe end. The top cap 1 extends outward to the skirt cap 2 with an outer skirt cap 4 to prevent the plug from being too deep inside. The bottom edge of the outer skirt cap 4 has a non-slip pad 5 to prevent sliding off, and reinforcing ribs 6 are set between the inner walls of the skirt cap 2, in a cruciform or T-shaped arrangement (as shown in Figure 1, the cruciform reinforcing ribs 6 are placed vertically). The overall structure is simple, easy to produce, provides good sealing, and is not easily dislodged during use, thereby extending the service life of stainless steel.