Abstract: This approach,under some plausible assumptions,introduces a new model on the yarn unevenness:fiber lane realignment model.A new parameter-fiber lane′s internal space is introduced,which represents both of fiber ends on the yarn cross section and the fiber length in a yarn.Using the same principle as Martindale′s,the model is applied to a sample of yarn unevenness and fiber length distribution.Thus an empirical forecasting equation is presented.The forecasting is conducted through number of fiber in yarn profile and upper half mean length(UHML) of fibers in yarn.The forecasting is proved to be effective.