The invention discloses a preparation method of three-dimensional dried flower. The preparation method comprises the following steps of 1, putting fresh flower to be treated into a dehydrant and carrying out dehydration treatment to obtain dried flower, 2, by a polypropylene plasticizer, carrying out vacuum dipping treatment on the dried flower obtained by the step 1 to obtain plasticized flower, and 3, carrying out hardening treatment on the plasticized flower obtained by the step 2. The preparation method of the three-dimensional dried flower adopts a plastination technology. Through dehydration, vacuum dipping and hardening treatment, the three-dimensional dried flower retains the original texture, color and components of the fresh flower, also retains the original graceful shape of the fresh flower, has lifelike appearance and a good ornamental value, has a certain toughness and elasticity, has no smell and no deformation, has stable quality, can be stored for a long time and is conducive to package, transport and exhibition. The preparation method can realize shaping treatment and plasticizing treatment on whole flowers and large flowers, provides a novel method for high-quality flower processing and has high applicability and a wide application scope.