Plastic pipe caps for protecting steel pipes, featuring a protective plug body that includes a top cap and a flange cap, the latter positioned at the bottom edge of the top cap. The top cap extends outward to the flange cap with an outer edge cap. A protective plug for steel pipe ends, comprising the plug body with a top cap 1 and a flange cap 2, where the flange cap 2 is located at the bottom edge of the top cap 1. The bottom外侧 of the flange cap 2 has a notched edge 3 for easy and quick placement in the pipe opening. The top cap 1 extends outward to the flange cap 2 with an outer edge cap 4, preventing the plug from being overly inward. The outer edge cap 4 has a non-slip pad 5 on its bottom edge around the flange cap 2 to prevent slippage. Inside the flange cap 2, there are reinforcing ribs 6, which are十字-shaped or I-shaped and can be placed either horizontally or vertically (as shown in Figure 1, where the十字-shaped reinforcing ribs 6 are placed vertically). The overall structure is simple, easy to produce, provides good sealing, and is not easily dislodged during use, thus extending the service life of stainless steel.