The invention provides a gold nanoparticle triangular plate preparing method and a method for preparing gold nanoparticle discs and gold nanoparticle hexagonal pieces on the basis of the gold nanoparticle triangular plate preparing method, relates to the technical field of gold nanoparticle preparing, and aims at providing the method which is easy and convenient to operate, high in repeatability and efficiency and is used for preparing gold nanoparticle triangular plates, gold nanoparticle discs and gold nanoparticle hexagonal pieces. The gold nanoparticle triangular plate preparing method includes the steps of preparing a gold nanoparticle seed solution through a sodium citrate aqueous solution, a tetrachloroauric acid aqueous solution and a sodium borohydride aqueous solution, preparing a gold nanoparticle triangular plate solution through the preapraed seed solution, a cetyl trimethyl ammonium bromide aqueous solution, a tetrachloroauric acid aqueous solution, a potassium iodide or sodium iodide aqueous solution, a sodium hydroxide aqueous solution and a ascorbic acid aqueous solution, and obtaining gold nanoparticle triangular plates after the liquid supermatant is abandoned. The method is easy and convenient to operate and high in repeatability and controllability, the prepared gold nanoparticle plates are unified in size, gold nanoparticle plates of different types and sizes can be synthesized, and the purity reaches 95% or higher.