The initial resistance of fabric to extension in warp or weft direction is theoretically studied by applying the same theory of extension used for crimped yarn axis, the form of which has been explained in the previous papers by the authors. Load (P) at extension (Δ/l1) is explained by the following equation.where, P: Load induced by extension (Δ/l1)(Δ/l1): Extensiona, l, n, m, : Parameter of yarn axis curve (m1′=m1+1)(EI): Bending rigidity of yarnp1: Crimp ratio of yarn extendedsufix 1……for extended yarn.sufix 2……for transvers yarn to extended yarn.These results are applied to three types of fabrics constructed equally and with yarns having different bending modulus. It is explicit that the above equation may be applied to the load-extension curves of fabric.