The invention provides a ternary compound modified bentonite material and a preparation method and application thereof. The preparation method of the ternary compound modified bentonite material includes: adopting dilute acid solution being 1-10wt% in concentration for acid modification of bentonite to obtain acid modified bentonite; adopting quaternary ammonium salt for organic modification of the acid modified bentonite, and after organic modification reaction is finished, adding polyhydroxy aluminum for inorganic modification into a system to obtain the ternary compound modified bentonite material. In application of the preparation method, by ternary compound modification of the bentonite, the advantage of high organic carbon content of organic bentonite is achieved on the basis that high thermal stability and specific surface area of inorganic pillared bentonite are kept. Therefore, the ternary compound modified bentonite material prepared according to the method is high in specific surface area, pore volume, interlamellar spacing and stability and high in practical wastewater adaptability and universality.