NOVELTY - Preparation of multifunctional solid super acid catalyst comprises ball milling graphite particles and silicon carbide particle and mixing to obtain graphite-silicon carbide mixture, putting zirconium(IV) oxychloride octahydrate, adding distilled water to fully dissolved to obtain solution, adding graphite-silicon carbide mixture in solution, putting powder-shaped 5A molecular sieve, adding water to trimethyl chlorosilane and dimethyl chlorosilane mixed solution, adding ultra-strong acid, stirring, vacuum drying at 50 degrees C for 5 hours, and vacuum cooling.    USE - Method of preparation of multifunctional solid super acid catalyst (claimed).    ADVANTAGE - The method can prevent water in the reaction system, and of free fatty acid.    DETAILED DESCRIPTION - Preparation of multifunctional solid super acid catalyst comprises:    (A) taking 0.1 mm diameter graphite particles and silicon carbide particle in ratio of 1:4, ball milling and mixing to obtain graphite-silicon carbide mixture, putting zirconium(IV) oxychloride octahydrate, adding distilled water to fully dissolved to obtain solution, adding graphite-silicon carbide mixture in solution, stirring and mixing uniformly at 400 revolutions/minute, using concentrated ammonia water to adjust pH to 8.2, generating coating of graphite-silicon carbide mixture of zirconium hydroxide precipitate when dripping ammonia water until no precipitate, standing for 24 hours for aging, repeatedly filtering, washing until no chlorine ion, obtaining filter cake to solid substance, vacuum drying, adding sulfuric acid solution at 30 degrees C while stirring and mixing for 24 hours under 200 revolutions/minute, separating and removing sulfuric acid solution, at 110 degrees C for 24 hours, obtaining solid matter at 550 degrees C under protection of nitrogen under normal pressure for 4 hours, and cooling to room temperature under protection of nitrogen to obtain microwave solid super acid; and    (B) putting powder-shaped 5A molecular sieve at 110 degrees C, vacuum drying for 10 hours in drying box, cooling to room temperature, adding trimethyl chlorosilane or dimethyl chlorosilane, vacuumizing, stirring for 5 hours, separating and removing molecular sieve, adding water to trimethyl chlorosilane and dimethyl chlorosilane mixed solution, adding ultra-strong acid at 30 degrees C, vacuumizing for 10 hours, stirring at 200 revolutions/minute, separating to obtain solid, vacuum drying at 50 degrees C for 5 hours, and vacuum cooling to room temperature to obtain multifunctional solid super acid catalyst.    An INDEPENDENT CLAIM is included for a synthesis of biological diesel oil comprising using catalyst, waste oil and methanol, adding in microwave reactor under normal pressure at 65-70 degrees C and 350 W, stirring to 600 revolutions/minute, reacting for 120-150 minutes, separating to remove catalyst to obtain crude product biological diesel oil, using distilled water to wash, obtaining oil phase, continuously decompressing and distilling to obtain biological diesel oil at 60-250 degrees C.