Abstract: To explore the mechanical properties of coarse-grained sulfate saline soil improved by pyrolysis residue of oil sludge, the effects of the content of pyrolysis residue of oil sludge on resilient modulus and unconfined compressive strength of coarse-grained sulfate saline soil are investigated through indoor tests. The results show that the resilient modulus and unconfined compressive strength of the improved coarse-grained sulfate saline soil increase first and then decrease with the increase of residue content under different salt content conditions. The most significant improvement of mechanical properties is observed when the residue content is 10%. The maximum resilient modulus is 245.52 MPa, and the maximum unconfined compressive strength is 0.48 MPa. The mechanical properties of the improved coarse-grained sulfate saline soil increase first and then decrease with the increase of salt content, and the improvement of mechanical properties of non-saline soil was more obvious than that of saline soil with the increase of residue content. According to X-ray diffraction(XRD) and scanning electron microscope(SEM) analysis, the improvement of coarse-grained sulphate saline soil by pyrolysis residue of oil sludge is mainly affected by physical and chemical factors. The friction of particles and the displacement of ions promote the strength of improved saline soil.