The invention relates to a preparation method of luminous poly(1,3-trimethylene terephthalate). 1,3 propanediol, a terephthalic acid and a nano illuminant-1,3 propanediol sol are polymerized; in an esterification reaction, the reaction temperature is 200-260 DEG C, the pressure is 0.1-0.5 Mpa, and the time is 60-180 minutes; in a polycondensation at a low-vacuum stage, the temperature is 200-290 DEG C, the pressure is gradually reduced from normal pressure to 0.1 MPa, and the time is 10-90 minutes; in a polycondensation at a high-vacuum stage, the temperature is 250-300 DEG C, the vacuum degree is 50-100 Pa, and the reaction time is 60-150 minutes; the intrinsic viscosity of the poly(1,3-trimethylene terephthalate) is 0.55-0.75 dL/g, and the fiber fabric of the the poly(1,3-trimethylene terephthalate) can emit light continuously for more than 12 hours in the dark under visible light irradiation; and the fabric of the the poly(1,3-trimethylene terephthalate) can emit light continuously for more than 12 hours in the dark within the same time of visible light irradiation after being washed 20 times in a standard manner.