The invention discloses an efficient terminalization preparation method for hydroxyl terminal nano diamond for biological application and belongs to the field of biological and medicinal functionalized basic material preparation. The method comprises the following process steps: a, performing mixed acid pickling, and washing a nano diamond powder turbid liquid to be neutral with deionized water; b, dissolving nano diamond powder and lithium aluminum hydride into a tetrahydrofuran solution, and putting into a high-temperature reaction kettle container till the volume of 60-90%; c, sealing an outer high-temperature reaction kettle steel sleeve, putting into a constant-temperature heating tank, and keeping a constant temperature; d, after a heat preservation time is met, cooling, taking out areaction after solution, and adding hydrochloric acid which does not react with diamond or tetrahydrofuran, but is used for dissolving metal ions instead; e, performing centrifugal separation, and washing the nano diamond powder with deionized water for multiple times till neutral without acid residue; and f, washing with acetone, and performing ethanol ultrasonic washing so as to obtain a hydroxyl terminal nano diamond turbid liquid, and performing dispersion purification, thereby obtaining high-quality hydroxyl terminal nano diamond. The method disclosed by the invention is convenient and simple and rapid in reaction velocity, and terminalization of a relatively large amount of nano diamond powder is achieved with solutions of same ratios and volumes.