Yarn made from natural fibers, synthetic fibers, or other types of fibrous materials is all formed by twisting an assembly of short or long fibers and its performance is significantly influenced by the physical behavior of these fibers in the yarn forming region-a small triangle area called spinning triangle. In spinning process, the fibers in spinning triangle where they are finally twisted into a yarn are subject to dynamic loads. However, earlier theoretical models are all based on the static assumptions and it cannot reflect the real status of the spinning process. Therefore, in this study, a new dynamic model of spinning triangle was developed by using finite-element method with consideration of the dynamic effects such as the inertia and damping forces of constituent fibers for a more complete and accurate description. With consideration of dynamic characteristics of fiber, earlier static model of spinning triangle can be considered as a special case of the proposed dynamic model. In order to verify the developed theoretical model, comparisons of the proposed model with earlier model and experimental measurements were carried out and good agreements were achieved. Furthermore, the dynamic behavior of fibers in spinning triangle, such as the natural frequency, mode shape, resonant response, harmonic analysis, and response under a time-varying tension, has been numerically studied. The results show that dynamic parameters have a great influence on the amplitude and attenuation of the response of constituent fibers in spinning triangle.