The bending properties of the single yarns, such as the bending rigidity, the coercive couple, the hysteresis energy, and the residual curvature, are related with their constituent fibre diameters as well as the surface helix angle antral the linear density. The estimated and the experimental values of these properties are compared by varying the blend ratio of wool/polyester fibres. The validity of the specific bending rigidity was ascertained by adopting the value, which the experimental bending rigidity of the single yarn is divided by experimental yarn linear density. The bending rigidity of single blend yarns depends on the number of yam twist, the linear density and the blend ratio. The specific bending rigidity was decreased with increasing the number of yarn twist and blend ratio of polyester fibre. The coercive couple and the residual curvature, relating to intra-fibre friction in the yarn, were increased with blend ratio of polyester fibre. The coercive couple and the residual curvature of 100% polyester staple yarn were increased with the twist angle, and the maximum of these values were found to be increased as the blend ratios of wool/polyester fibres were increased.