Abstract: During the course of texturing, the entropy of the filaments structure system was increased. Corresponding changes in its bending stiffness always occurred with this phenomenon at the same time. To quantitative analyze the relationship between the entropy changing and stiffness changes of a linear model during texturing, cantilever measuring was used to measure the bending rigidity of the textured yarns while the EIB to test their diameter and then the relative entropy value were told. The results showed that air-texturing could rise the relative entropy value from 0.3 to 1.45 while the disordering degree 1.28 to 4.25; further differential shrinking would increase the relative entropy value to 1.65, as well the disordering degree to 5.00 and so on. The increasing disordering degree of the filaments’ fragments led to the forming and enlarging of the disordering structure and entanglement structure, which was shown by the rapid rising of bending stiffness and worse handle of ATY; by multi-texturing the entanglement structure might be adjusted and lower bending stiffness might be then.