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In the present work, we report a simple, economic and template-free strategy to synthesize macroporous SiO2 as catalyst support for soot combustion. The textural structure of SiO2 could be manipulated effectively to facilitate soot combustion through controlling the agglomeration and growth of colloidal silica particles in the sol-to-gel process. The Brownian motion, the inter-particle distance and the electric double layer of colloidal silica particles, all exert great influence on the porosity of the finally formed SiO2 at the molecular level. The texture characterizations indicate that considerable amount of macropores could be generated in the prepared SiO2 sample. The macroporous structure of SiO2 promotes the soot combustion efficiency greatly, since it can provide accesses for soot particles entering inner pores and interact with inner-surface active centers. Moreover, upon loading Ag2O, Na2O or K2O on the as-prepared macroporous SiO2 support, excellent activity for soot oxidation was obtained. The strategy proposed in the present work has great application potentials for soot combustion reactions and other processes demanding efficient contact in gas-solid-solid reactions.