The whole process of plant oil conversed to biodiesel is closed-circuit circulation, all raw material comprehensive utilization, cleaner production. Roughly described as follows: Raw material pretreatment (dehydration, deodorization, purification )—–the reaction kettle (methyl ester+ alcohol catalyst + 70℃) —–stirring reaction N hours—-precipitation separation line of mixed alcohol—-methyl distillation—-recovery of alcohol—-methyl ester distillation—-finished product.