The invention discloses extinction polyamide-6 and a preparation method thereof. The method comprises the steps that TiO2 powder is added into water, a dispersing agent and a pH conditioning agent are added, ultrasonic treatment and mechanical stirring or grinding and even mixing are conducted, standing is conducted for layering, centrifugation is conducted to separate supernatant, and an ultra-fine TiO2 suspension is obtained; the ultra-fine TiO2 suspension is added into a polyamide-6 polymerization system, an in-situ polymerization reaction is conducted, extrusion granulation is conducted, and the extinction polyamide-6 is obtained; TiO2 granules in the prepared extinction polyamide-6 are uniformly dispersed, and the granule diameter ranges from 0.050 micrometer to 0.250 micrometer. According to the preparation method of the extinction polyamide-6, dispersion stability of the TiO2 suspension is improved, other impurities are not introduced, the product is pure, the TiO2 granules in a prepared extinction polyamide-6 slice are uniformly dispersed and small in granule diameter, the slice is uniform in luster, stable in quality and good in extinction effect, compatibility between the TiO2 granules and a polyamide-6 substrate is improved, and the spinnability is good.