Abstract: Having constructed a single yarn with different cross sections 3D model,a concave-convex type turbulence is exerted randomly on the cross sections while rotating the sections along the radial direction of the yarn so that a wave-like twist effect is generated on the yarn.This is equivalent to the 3D bumping texture being inserted on the surface of the yarn,improving the vividness of the simulated yarns,especially to the yarn with a nearly round cross section.