The utility model relates to a multi -functional integrated preparation of bio -diesel device, including preceding processing apparatus, reaction unit, methyl alcohol recovery unit, water separation washes device and dewatering device, preceding processing apparatus is arranged in getting rid of the visible particle of grease, preceding processing apparatus's output passes through pipe connection to reaction unit input, reaction unit connects methyl alcohol recovery unit respectively through the pipeline and water separation washes the device, methyl alcohol recovery unit links to each other with dewatering device, this preparation facilities is applicable to the waste oil of different acid numbers, satisfy simultaneously that one step of method of esterifying and two steps are esterified in advance and the lactide legal system is equipped with the required condition of biodiesel, when one step of legal system of esterifying is equipped with biodiesel, can two sets of reactions expand simultaneously, and do not influence final result, compared with the prior art, the utility model, each reaction unit loops through the pipeline and the integration of power conveyor is connected, and A number of processes combines in proper order, can be applied to regional interior waste oil's regeneration among a small circle and prepare out high -quality biodiesel.