Abstract: Introduced the specific demands of sizing worsted wool yarns.Sizing performance of commonly used three kinds of size on wool yarn,e.g.,cohesiveness,wettability,compatibility,and film-forming was examined and compared.And compounding experiments were carried out with PVA0588,modified starch ASP,polyacrylamide size at different mixing ratio,using penetrant BX,JFC,T selectively. The test results show that determination of proper component proportion of mixed size and addition of appropriate amount of penetrant are factors for ensuring favorable sizing performance of the mixed size and better sizing effect on worsted wool yarns.