In cotton weaving industry, efficiency of loom shed is highly influenced by the quality of weaving preparatory processes. During sizing, core yarn strength has been improved at significant level along with preserving its elongation property. Whereas higher end breakage rate in warping leads to generation of lappers during sizing and it a reason for weavers beam quality. This paper presents an investigation consisting of several stages of sample treatment and testing. The first stage was warp is prepared in a sectional warping machine on cotton yarns (with nominal counts of 20ne and 30ne). Differences in physical and mechanical properties between yarns of different were then investigated. In the second treatment stage all samples were sized using two processes: the standard sizing process and pre-wetting sizing process, with same size concentrations, with the aim to investigate the influence of the sizing process on warp. Also, the influence of conventional sizing process over pre-wet sizing process will make any impact on sizing cost and energy reduction are studied. Also, the weaving efficiency was studied on the rapier auto loom that both conventional sizing and pre-wet sizing will make any impact. Well as on physical-mechanical properties of sized yarns required for weaving is studied and concluded that will increase the weaving performance, which are of paramount importance for the further process of making a woven fabric.