It is difficult to employ the parallel model or the steel strand model based on the assumption of parallel wire to analyze the mechanical properties of the semi- parallel cable due to its helical characteristics and special structure.In this paper,a nonlinear equation of multilayered semi- parallel cable under the static tensile load is de-rived based on the theory of Love's curved bar and by considering the effects of the bending moment,the torque and the Poisson effect.Moreover,the effects of the helical angle on the axial force,the torsion,the axial stiffness and the distribution of the tensions between wire layers are discussed in detail.Numerical results show that,with the in-crease of the helical angle,both the axial force and the axial stiffness increase,the torque first increases and then decreases,and the distribution of the tensions between wire layers tends to be uniform.