The invention relates to a preparation method of a saturated soil sample in a geotechnique dynamic centrifugal model test. The preparation method comprises the following steps of drying a field soil sample, crushing, and screening the field soil sample through a geotechnique sieve; calculating the needed water amount after the saturated moisture content tested by a conventional geotechnique test is increased to a certain extent, stirring and preparing the saturated soil sample in a vacuum stirring machine; uniformly loading the saturated soil sample into a model box, and embedding a porosity water pressure sensor in the soil sample; laying an isolation layer on the top of the saturated soil sample, uniformly laying dry sand with a given thickness on the isolation layer, and uniformly putting the prepared bagged dry sand on the dry sand layer; hoisting the model box, starting a centrifugal machine after the model box is fixed, and solidifying the saturated soil sample after a designed acceleration is reached; judging the stopping time through the embedded porosity water pressure sensor, stopping the machine, and hanging out the model box after the initial excess pore pressure is completely dissipated; and repeating the operation until the entire model is prepared. By adopting the preparation method, the saturation time of the soil sample can be shortened, the secondary application problem of the soil sample caused by the limit for taking soil on a field can be solved, the centrifugal solidification time can be shortened, and the solidification ending time can be accurately judged.