摘要： Due to the fact that the relationship between the extrudation moisture regain of sized yarns and size pick-up is expressed only by an approximate equation,and which is not suitable for prewetting sizing process,accurate equations to express the relationships between the extrudation moisture regain of sized yarns and size pick-up for traditional sizing process(including high-pressure sizing) and prewetting sizing are derived.When the prewetting sizing has the same extrudation moisture regain of sized yarns and the same size concentration as the traditional sizing process,prewetting sizing leads to lower size pick-up.The deviation of the extrudation moisture regain obtained by the approximate equation increases with increasing of size concentration.