Sulfonic acid group-functionalized amorphous carbon solid acid catalyst (AC-SO3H) was prepared through vapour-phase transfer sulfonation method. The material was characterized by means of inductively coupled plasma atomic emission spectrometry (ICP-AES), Fourier-transform infrared spectrum (FT-IR), X-ray powder diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric analysis (TGA). Elemental analysis result shows that the obtained solid acid catalyst has a —SO3H group loading of 2.03 mmol/g. Comparing with other solid acid catalysts, AC-SO3H shows enhanced activity and proves to be efficient heterogeneous catalyst for Baeyer-Villiger oxidation of ketones and Friedel-Crafts alkylation of anisole with benzyl alcohol. The catalyst shows excellent thermal and structural stability, and retains good activity over several cycles. The synthesis process is simple and the catalyst can be easily prepared in large scale.