The Box-Behnken response surface method is adopted to study the mixing proportion of synchronous mortar cementing materials prepared by waste mud of slurry shield with cement and that with fly ash, and the optimal mixing proportion is determined. The hardening mechanism of inorganic binder-waste mud composite cementing material is analyzed by X-ray diffraction(XRD) and scanning electron microscope(SEM), and the analytical results indicate that the peculiar microstructure of waste mud of slurry shield accelerates the inorganic binder hydration and hardening reaction, which can help increasing the paste strength. The proposed inorganic binder-waste mud of slurry shield can be used as the cementing material of slurry shield synchronous mortar in similar projects in the future.