The invention relates to a preparation method of antistatic polytrimethylene terephthalate. The preparation method comprises adopting 1, 3-propanediol, terephthalic acid and nano antistatic agent-1, 3-propanediol sol to perform polymerization; enabling reaction temperature of an esterification reaction to be 200-260 DEG C, enabling reaction pressure to be 0.1-0.5 MPa, and enabling reaction time to be 60-180min; enabling low-vacuum polycondensation reaction temperature to be 200-290 DEG C, reducing reaction pressure gradually from normal pressure to 0.01MPa, and enabling reaction time to be 10-90min; and enabling polycondensation reaction temperature at a high-vacuum stage to be 250-300 DEG C, enabling vacuum degree of a reaction system to be 50-100Pa, and enabling the reaction time to be 60-150min. The intrinsic viscosity of the polytrimethylene terephthalate is 0.55-0.75dL/g, the volume resistivity is 108 ohms/cm-109 ohms/cm, and the specific resistance is unchanged after a fabric undergoes standard washing for 20 times.