Abstract: ObjectiveThe low mechanical strength, high water content, non-uniform particle distribution, and poor engineering controllability of original mucky soil in practical engineering projects are addressed through the utilization of industrial solid waste such as slag and phosphogypsum. Method The slag, phosphogypsum, and cement are combined to formulate a soil stabilizer, which is used in laboratory tests to investigate the influence of stabilizer dosage on the mechanical properties of mucky soil and to conduct a mechanism analysis. Result The improved mucky soil exhibits favorable mechanical properties. At the optimal stabilizer dosage of 8%, the unconfined compressive strength, internal friction angle, and CBR value of the stabilized mucky soil specimens reach their peak values, followed by a slight decline with increasing stabilizer dosage. The swelling capacity reaches its minimum when the optimal stabilizer dosage is achieved. In contrast, the cohesive force consistently increases with the rising stabilizer dosage. X-ray diffraction and scanning electron microscopy analyses reveal that the addition of phosphogypsum composite soil stabilizer promotes the generation of hydration products such as ettringite (AFt) and calcium silicate hydrate (C-S-H), enhancing the agglomeration of stabilized mucky soil particles, acting as a binder, and partially filling voids, thereby improving the mechanical solidification performance of the soil. Conclusion Explore the effect of applying industrial solid waste to improve the mechanical properties of silt, and further lay the foundation for the comprehensive utilization of industrial solid waste in transportation engineering fields such as roads.