The invention belongs to the technical field of chemical industry production and provides a method and a device for preparing an aluminum hydroxide powder by an esterification reaction. The method includes mixing an organic acid and an organic alcohol and adding alcohol aluminum to obtain a mixture, and heating and back flowing the mixture for 3-12 hours; finishing a reaction, naturally cooling the mixture to the room temperature, and pouring out a liquid layer on the upper portion to reserve as an esterification product; and subjecting white precipitation at the bottom and a small amount of solution to a centrifugal separation at a rotating speed of 4000 revolutions per minute, washing by a 95% (v/v) of ethanol and an absolute ethyl alcohol, and drying for 4-8 hours in a vacuum drying box at the temperature between 80 DEG C and 100 DEG C. According to the method, a preparation for an aluminum hydroxide superfine powder can be one-time completed in a liquid phase, alkoxide can be slowly hydrolyzed by water molecules generated by the esterification reaction, an additive is not needed, an aftertreatment process is simple, the appearance of a product is regular, the water molecules generated by the esterification reaction can be consumed by the alkoxide hydrolysis, so that an equilibrium shifting of the esterification reaction is promoted, the extent of the esterification reaction is accelerated, the reaction time is shortened, and the method and the device have high popularization and application values.