<p>Clay exhibits strong water sensitivity and low strength, making it highly susceptible to undesirable phenomena in engineering applications. To address this issue, the enhancement of soil properties through the addition of solidifying materials is considered, particularly in light of the low utilization rate of phosphogypsum slag. Therefore, phosphogypsum is employed as a PS cementitious material (comprising phosphogypsum, slag, and calcium oxide), combined with basalt fiber (BF) as a novel green material to synergistically solidify the soil. The effects of fiber content, PS content, and curing time on the performance of the solidified soil were investigated through various tests, including compaction tests, unconfined compressive strength tests, Brazilian split strength tests, falling head penetration tests, scanning electron microscopy, and X-ray diffraction tests. The results indicated that as the PS mix content and curing time increased, the compressive strength of the soil gradually improved and exhibited significant brittleness. The strength of the PS-solidified soil could reach 2118&#xa0;kPa at 28 days, representing a 1340% enhancement compared to that of raw soil. An optimal fiber content was identified in the PS-BF solidified soil (0.6% BF), which resulted in a 54% increase in strength compared to PS solidified soil. As fiber content increased, the energy absorption capacity initially rose and subsequently declined, while the permeability coefficient exhibited the opposite trend. The fibers and the hydration products adhering to the surface collaboratively contribute to the strengthening of the soil. These research findings can provide theoretical and technical guidance for subgrade improvement and slope protection.</p>