The geometrical structure of 2-ply multifilment yarn was assumed, in order to investigate the bending properties of 2-ply multifilament yarn. And angle, Ψ between single filament in the single strand and strand axis was derived by considering the changes of torsion of constituent filaments of the single strand. The angel, Ψ was expressed as a function of plying helix angle, $alpha$p, filament helix radius, ${gamma}$, and traverse rotation angle, $Phi$2 of constituent filament in the single strand.