The dredged soil of waterway is increase day by day, and the utilization of dredged soild to make spray seeding matrix for slope greening can realize the resource utilization of dredged soil. The L₂₅(5³) orthogonal test design was adopted with dredged soil as the main test material, and different proportions of PAM, SAP and straw were added to the dredged soil for improvement, and tall fescue was planted for pot experiment. The physical structure characteristics, moisture characteristics, chemical properties and tall fescue emergence rate of each test group were measured. The effects of PAM, SAP and rice straw on the dredged soil were analyzed. Through the comprehensive evaluation of the principal component analysis method, the ratio of the green spraying substrate based on the dredged soil was obtained. The results show that adding SAP to the dredged soil can significantly improve the pore characteristics of the dredged soil, reduce the soil bulk density, and increase the water holding capacity of the dredged soil; an appropriate amount of PAM can increase the retention of ammonium nitrogen in the dredged soil and promote tall fescue seeds. Excessive PAM will inhibit the germination of tall fescue seeds; straw can significantly increase the nutrient content of the dredged soil and reduce the pH value of the dredged soil; the optimal ratio of the substrate is 6 g of sap, 0.5 g of PAM and 35 g of straw per kg of dredged soil.