In this paper, a new type of LLDPE/nano CaCO3 composite based artificial turf yarns with good tensile property and UV resistance is introduced. The effect of nano CaCO3 content on tensile properties shows that the tensile force reached the maximum value when the CaCO3 content is about 7wt%, and the elongation at break gets to the highest point at 10wt%. After 3000h UV accelerated aging, the nano-CaCO3 and LLDPE based artificial turf fiber yarns has tensile strength retention about 87%, and the elongation at break is higher than LLDPE. DSC results shows that with the increase of nano-CaCO3 content, the crystallization temperature gradually increased, and the crystallinity degree declined. SEM images of cross sections of monofilament fibers show that nano CaCO3 had a good dispersion in monofilament fiber matrix. These reasons give rise to the improved mechanical properties of turf yarns.