Phosphorus slag concrete without plastic steel fiber was used as the reference. Taking plastic steel fiber as the research object, four-point bending tests were carried out on plastic steel fiber phosphorus slag concrete with fiber length of 30 mm, 40 mm, 55 mm and fiber content of 3 kg/m3, 6 kg/m3 and 9 kg/m3 to study the influences of different fiber length and fiber content on the bending properties of phosphorus slag concrete. The results show that the bending strength of phosphorus slag concrete increases with the increase of the length and content of plastic steel fiber. When the length of plastic steel fiber is 55 mm and the content of plastic steel fiber is 3 kg/m3, the bending strength of phosphorus slag concrete is the best, and the bending strength is 56% higher than that of the reference group. With the increase of length and content of plastic steel fiber, the bending toughness index and bending toughness of phosphorus slag concrete increase continuously. When the length of plastic steel fiber is 55 mm and the content of plastic steel fiber is 9 kg/m3, the bending toughness index I20 is 9.8 times higher than that of the reference group.