NOVELTY - A sulfuric acid-acidified mesoporous silica (SiO2) colloidal sphere catalyst is prepared by stirring cetyltrimethylammonium bromide (CTAB) and anhydrous ethanol in beaker until CTAB is completely dissolved, stirring phosphomolybdic acid and anhydrous ethanol using glass rod in other beaker until phosphomolybdic acid is completely dissolved, dropwise adding phosphomolybdic acid solution to CTAB solution while stirring in which molar ratio of CTAB and phosphomolybdic acid is 3:1, continuously stirring for half an hour, filtering, and drying.    USE - Preparation of sulfuric acid-acidified mesoporous silica colloidal sphere catalyst for synthesis of biodiesel (claimed).    ADVANTAGE - Catalyst has high efficiency and good catalytic activity and stability, and is non-corrosive and environment-friendly.    DETAILED DESCRIPTION - A sulfuric acid-acidified mesoporous SiO2 colloidal sphere catalyst is prepared by stirring CTAB and anhydrous ethanol in beaker until CTAB is completely dissolved, stirring phosphomolybdic acid and anhydrous ethanol using glass rod in other beaker until phosphomolybdic acid is completely dissolved, dropwise adding phosphomolybdic acid solution to CTAB solution while stirring in which molar ratio of CTAB and phosphomolybdic acid is 3:1, continuously stirring for half an hour, filtering, drying to obtain cetyl trimethyl quat.-ammonium phoshomolybdate (M-6), ultrasonically dispersing 70-180 mg M-6 and 15-60 ml anhydrous ethanol in round bottom flask for 30 minutes until solid is completely dispersed, dropwise adding 45-80 ml distilled water, stirring at constant temperature for 6 hours, adding 0.14 ml aqueous ammonia and 0.05-0.2 ml ethyl orthosilicate, continuously stirring at constant tem for 16 hours, filtering, drying, calcining in muffle furnace at 450 degrees C at heating rate of 1 degrees C/minute for 4.5 hours to obtain mesoporous SiO2 colloidal sphere catalyst which is white solid, stirring with 0.5-1.5 M sulfuric acid (H2SO4) in round bottom flask for 20 minutes, filtering, and drying.