The invention relates to a functional industrial yarn and a preparing method thereof. The preparing method includes the steps of extruding a high-molecular-weight polymer melt with a functional additive out of a spinneret orifice at the shearing rate of 1000-1500 s<-1>, then conducting slow cooling and cooling to prepare the functional industrial yarn, and meanwhile adjusting the process parameters such as the melt temperature, slow cooling temperature, slow cooling area height and cooling wind speed and wind temperature. The functional additive in the finally-prepared functional industrial yarn is evenly dispersed and distributed and is even in radial structure and excellent in performance. The functional additive in the functional industrial yarn has the statistical average size difference smaller than or equal to 50 nm and the maximum size difference smaller than 100 nm compared with the functional additive not added to the high-molecular-weight polymer melt. The difference betweenthe content of the functional additive on the surface layer of the functional industrial yarn and the content of the functional additive at the center of the functional industrial yarn is smaller than0.5 wt%. The method is simple, industrial popularization is easy, and the comprehensive performance of the functional industrial yarn is effectively improved.