NOVELTY - Producing biodiesel involves performing diazo-coupling reaction by adding water in 20000 l stainless steel reaction kettle, then adding para-amino-methyl amide with hydrochloric acid, stirring, adding sodium nitrite, adding sulfamic acid to remove redundant diazonium salt, and then adding auxiliary agent, water and ice; and after coupling adding water in kettle, then adding sodium hydroxide, adding azoic acid, stirring for, and then adding calcium chloride and water, raising temperature to 65-80 degrees C.    USE - For producing biodiesel (claimed).    ADVANTAGE - The method provides product with high product, and good quality; and saves water.    DETAILED DESCRIPTION - Producing biodiesel having Permanent high F5RK (pigment international index number: C.1.Pigment Red 170; CAS Accession No.: 2786-76-7.) by Lewis acid catalytic one-step process involves using para-amino-methyl and naphthol as raw material, and using water as solvent, performing diazo-coupling reaction by adding 2500 l water in 20000 l stainless steel reaction kettle, then adding para-amino-methyl amide with hydrochloric acid, stirring, rotating at a speed of 70 revolution/minute, stirring for 10-15 minutes, adding ice to 1800 parts by mass, adding 135-149 parts by weight sodium nitrite, stirring for 60 minutes, adding sulfamic acid to remove the redundant diazonium salt, and then adding auxiliary agent, 46-47 parts by weight (pts. wt.) water and 800 pts. wt. ice, stirring; and after coupling adding water in stainless steel reaction kettle, then adding 795-915 mass% sodium hydroxide, stirring, heating at 70-75 degrees C, adding 609-663 parts by mass the azoic acid, stirring for 10-15 minutes, raising the temperature to 50 degrees C, measuring the pH value, then adding 53-59 parts by mass rosin, 29-32 parts by mass sodium hydroxide and 220-550 parts by volume water, measuring the pH value, and then adding 23-24 parts by mass calcium chloride and 200-300 parts by volume water, raising temperature to 65-80 degrees C, to obtain biodiesel.