The non-linear equations of motion,in which the static sag,bending rigidity as well as the geometric no-linearity is considered,are promoted.Several numeric examples of typical inclined cables are prosecuted by using L-P method and harmonic probing method.The results demonstrate that the frequency is related to the original force,the sag of cable,bending rigidity,inclined angle and the influnce of original force is the obviousest.