The invention relates to a PTT ((polytrimethylene terephthalate) low stretch yarn with wool-like effect and preparation method thereof. The cross section of the PTT low stretch yarn is nine-teeth shaped, and the low stretch yarn particularly comprises a core part with circular cross section and nine teeth parts uniformly distributed along the circumferential direction of the core part, wherein a groove with depth H of 0.04-0.08mm is formed between two adjacent teeth parts; and the PTT low stretch yarn is made by raw materials of PTT sections with viscosity of 0.92-1.0 and viscosity average molecular weight of 25000-30000. Different from the traditional method of changing the fiber components to achieve the wool-like effect, the wool-like effect of the low stretch yarn in the invention is achieved by designing the cross section of the PTT low stretch yarn. The dark and wool-like effect of the PTT low stretch yarn with nine-teeth shaped cross section is achieved by the diffuse reflection function for the beam; meanwhile, the stiff and smooth effect of the fiber are endowed through the axial groove skeleton effect. By adopting the preparation method of the PTT low stretch yarn, the PTT low stretch yarn with obvious hole and groove is successfully produced by a specific spinneret plate under production conditions, and the excellent wool-like effect is obtained.