The mix ratio of thixotropic slurry in pipe jacking is mostly determined based on experience, and engineering geological conditions are hardly considered in the mechanism analysis of the correlation between slurry composition and properties. To address these issues, a pipe jacking project traversing silty clay layers in Nanjing was studied, and a slurry performance evaluation index system was established. The optimum Na₂CO₃ dosage was determined through mix ratio testing, and a grey similarity absolute correlation model was employed to analyze the correlation between bentonite, carboxymethyl cellulose (CMC), and slurry performance indexes. The results indicate that the optimal Na₂CO₃ dosage (relative to bentonite) maximizes the rheological properties of the slurry, and this percentage depends solely on the montmorillonite content in bentonite. Thixotropy serves as the most reasonable index for determining this percentage. Bentonite exhibits stronger correlations with thixotropy and fluid loss of slurry, while CMC, as a tackifier, shows a higher correlation with Marsh funnel viscosity. Both components have comparable effects on the dynamic shear force.