The invention discloses a tubular continuous method for preparing beta-menadione, which comprises the following steps: preparing a beta-methylnaphthalene emulsion, heating the beta-methylnaphthalene emulsion, metering the beta-methylnaphthalene emulsion and an oxidation solution respectively by a measuring pump, adding into a tubular reactor provided with an ultrasonic generator, and carrying out ultrasonic reaction, wherein the retention time of the reactants in the tubular reactor is 1-300 minutes; supplementing dilute sulfuric acid to the outlet of the tubular reactor, adding into a curing tank, and curing for 1-10 hours while keeping the temperature; after finishing curing, filtering, washing, carrying out centrifugal dehydration and drying to obtain the beta-menadione finished product. By using the tubular reactor to produce the beta-menadione, the method has the advantages of high production continuity and short period; and the product has the advantages of high yield, low impurity content and stable quality. The reaction process is easy to control, simple to operate and high in automatic control degree; the material performs forced flow in the tubular reactor to substitute mechanical stirring, thereby implementing industrialized continuous production; and thus, the method has the characteristics of low input cost and short reconstruction period, and can perform large-scale industrial production.