The invention discloses a reaction treatment method of heliotropin intermediate 3,4- dioxymethylene mandelic acid. The method comprises the following reaction treatment steps: firstly, adding glyoxylic acid in a reaction kettle, adding 1,3-benzodioxole under stirring action, and cooling the glyoxylic acid and 1,3-benzodioxole mixed liquid with brine ice; adding a catalyst, namely concentrated sulfuric acid; then dripping a water-insoluble inert solvent, namely dichloromethane, into a head tank, carrying sampling detection on a reaction mixture, and stopping reaction when the content of 1,3-benzodioxole in the reaction mixture is not reduced any more; and finally, adding water into the reaction kettle, uniformly stirring, discharging and filtering by suction to obtain the solid material, namely 3,4- dioxymethylene mandelic acid. According to the reaction treatment method, the feeding sequence is regulated in the early stage to improve the mixing effect and increase the reaction speed, and the water-insoluble inert solvent is added to dilute the reaction mixture, so that the stirring effect is not influenced, the reaction time is shortened, and the problem of hard stirring in the late reaction stage can be solved.