NOVELTY - A multi-series fixed bed solid acid bio-diesel producing method involves pre-heating raw material oil and methanol by a heater (6) and reacting with esterification solid acid catalyst in a primary fixed bed esterification reactor (7). The reactor is connected with a static separator (8) to separate out resin from a jar. The processed resin is transferred to a falling film evaporator (10) to remove the methanol and water, and transferred into a decoloring tower (15) to be decolored. The decolored resin is transferred into a bag-type filter (16) to obtain fatty acid methyl ester.    USE - Method for producing multi-series fixed bed solid acid bio-diesel.    ADVANTAGE - The method enables producing biological diesel oil through continuous flip-flop esterification of waste oil and the methanol by utilizing multiple sets of fixed bed and separator combination components of a multi-series fixed bed solid acid bio-diesel production device. The multi-series fixed bed solid acid bio-diesel production device is convenient to carry and install and ensures continuous biological diesel oil production at normal temperature and normal pressure. The device is made of carbon steel, so that the device is inexpensive and environment-friendly, and has high return efficiency, and saves energy.    DETAILED DESCRIPTION - A multi-series fixed bed solid acid bio-diesel producing method involves making raw material oil and methanol in volume ratio of 9:1 to be placed in a jar. The raw material oil and methanol is pre-heated by a heater and reacted with esterification solid acid catalyst in a primary fixed bed esterification reactor. Temperature is controlled between 55-65 degrees C. The fixed bed esterification reactor is connected with a static separator to separate out resin from the jar. The separated resin is mixed with methanol in weight ratio of 9:1 and reacted with the esterification solid acid catalyst in a secondary fixed bed esterification reactor. The reaction is continued in third, fourth, fifth and sixth fixed bed esterification reactors. The processed resin is transferred to a falling film evaporator to remove the methanol and water, and transferred into a decoloring tower to be decolored. The decolored resin is transferred into a bag-type filter to obtain fatty acid methyl ester. An INDEPENDENT CLAIM is also included for a multi-series fixed bed solid acid bio-diesel production device.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic illustration of a multi-series fixed bed solid acid bio-diesel producing method.    Heater (6)    Primary fixed bed esterification reactor (7)    Static separator (8)    Falling film evaporator (10)    Decoloring tower (15)    Bag-type filter (16)