Abstract: To address shoreline erosion and ecological degradation in the middle reaches of the Yangtze River, an ecological restoration technology was proposed. This technology uses slag sulphoaluminate cement (SSAC) and chitosan (CS) to synergistically solidify the bank slope surface clay. It targets the poor ecological compatibility of traditional rigid revetments and the high carbon emissions of ordinary cement solidifying agents. The engineering characteristics and microscopic mechanisms of the solidified soil were systematically investigated through unconfined compressive strength tests, static and dynamic disintegration tests, along with XRD, SEM, and NMR microscopic analyses. The results indicate that the optimal mass ratio of sulphoaluminate cement to slag in the SSAC system is 85∶15. The effect of CS on the strength of the solidified soil exhibits significant age and dosage dependence. After 28 days of curing, the strength of the solidified soil with 1% CS increased by 14.9%. Furthermore, CS has a more significant impact on water stability. It not only delays the disintegration time of the soil but also enhances its resistance to water flow erosion. The strength of the soil can still reach 1.7 MPa after 210 minutes of scouring. The comprehensive water stability coefficient evaluation shows that a 1% CS dosage yields the best anti-erosion performance. Microscopic mechanisms reveal that the ettringite and C-S-H gel generated by SSAC hydration construct a large-pore rigid skeleton within the soil, while CS forms a flexible fiber network between particles to fill the micro-pores. This study can provide technical support for the ecological restoration of bank slopes in the middle reaches of the Yangtze River.