Abstract: This paper developed a mathematical model to investigate the dynamics of low(negative)tension cable, in which bending moment plays an important role in cable dynamics. Lumped mass method(LMM) was employed to describe the cable dynamics, a new three dimensional scheme was proposed to compute the bending momentinduced load from the relationship between moment and distributed load, which was then incorporated into the governing equation of LMM, the equation was solved by the 4th order RungeKutta integrating procedure. Numerical cases were presented for lowspeed towing, which illustrate that the effect of bending moment can not be neglected in order to get reasonable result, and also validate the proposed scheme.