The morphology of the platinum (Pt) nanoparticles has a significant effect on their activity for the catalytic oxidation of the volatile organic compounds (VOCs). In this work, the preparation of the dendritic and spherical Pt by a solution-based approach is reported, which is supported on -Al2O3 substrates, for decreasing the temperature of the complete conversion of benzene, one of the representative contaminants among the VOCs because of its carcinogenicity. The X-ray photoelectron spectroscopy analyses reveal that the surface adsorbed oxygen is crucial for catalytic performance, and the electron transference from Pt to O is a benefit for the activation of oxygen. H-2-TPR results indicate that the reducibility of the catalyst has a significant effect on the catalytic activity for the catalytic oxidation. In general, the dendritic Pt/Al2O3 catalysts, which possess more abundant and active surface adsorbed oxygen, exhibit the higher activity for the complete catalytic conversion of benzene compared with the spherical one. Moreover, the addition of a small amount of Ag (or Au), which is in order to ensure the dendritic structure, has little influence on the catalytic activity. The versatile solution-based synthesis will be a promising method for creating the highly efficient catalysts for environmental remediation.