First, γ-glycidyl ether propyl trimethoxysilane (KH560) and diethylenetriamine (DETA) were used as raw materials to synthesize a novel multi-amino silane modifier (AS) through a ring-opening addition reaction. Next, the mesoporous silica (SiO2) carrier was prepared by acidification, calcination and pore-creation in natural wollastonite. Finally, amino-functionalized mesoporous SiO2 composites (AS/SiO2) were obtained by grafting AS onto the surface of the mesoporous SiO2 carrier. The samples were characterized using techniques such as X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The static and dynamic adsorption performance of AS/SiO2 for CO2 capture under different loading conditions was investigated, and its adsorption mechanism was studied. The results indicated that AS was bonded to the surface of the mesoporous SiO2 carrier in the form of the chemical bond. Compared to SiO2, the AS/SiO2 composite significantly improved the CO2 adsorption capacity and breakthrough time. When the AS loading was 10%, the equilibrium CO2 adsorption capacity of the AS/SiO2 composite was 123.4 mg/g.