The invention discloses a preparation method of calcium phosphate nanopowder with a controllable length-to-diameter ratio and calcium-to-phosphorus ratio. The method comprises the step: carrying out areaction by mixing phosphate or phosphoric acid with a calcium salt to prepare the calcium phosphate nanopowder, wherein the one-dimensional size of a calcium phosphate nanoparticle can be regulatedto be 50nm-5mu m and the length-to-diameter ratio can be regulated to be 2-50 by adding a pH regulator into a reactant, components and proportions of the calcium phosphate nanopowder serving as a product can be regulated by controlling the feeding ratio of the phosphate or phosphoric acid to the calcium salt to be 1.5-1.67, and the calcium phosphate nanopowder is beta-tricalcium phosphate and/or hydroxyapatite. According to the method disclosed by the invention, the length-to-diameter ratio of the product is regulated by controlling the proportion of weak bases and relatively strong bases in the pH regulator; the calcium-to-phosphorus ratio of the product is controlled by changing the feeding ratio of a calcium source to a phosphorus source; a supergravity technology is combined to enhancea micromixing effect, so that the calcium phosphate nanopowder is prepared; and the preparation method is low in production cost, simple in operation, good in repeatability, better in application performance and wider in application range.