Abstract: This paper adopts nonlinear vibration method to analyze the fluctuation process of warp yarn during weaving and Kelvin model to analyze the constitutive relation of its visco elasticity.A differential equation of warp yarn vibration in lengthwise and crosswise is established based on Newton law.Using variable-separating method,it separates time variable from space variable,and Galerkin equation of discrete motion is used in discussion on the change trend of stable zone of the transition curve.And the numerical solution of the equation of motion is obtained using 4-order Runge-Kutta method.Furthermore,the effect of material properties of warp yarn and various parameters on the crosswise motion of the yarn is investigated,and the method to control the vibration of warp yarn is given.