The stability of principal parametric resonance of stayedcable caused by axial excitation is investigated. Nonlinear equations of vibration, in which the static sag as well as the geometric nolinearity is considered, are firstly derived. Then, the method of multiple scales is applied to the differential equation to analyze the principal parametric resonance of stayedcable and the stability of the steady solutions is also investigated in detail. Finally, numerical simulation is used to study the principal parametric resonance of stayedcable. The time histories of stay cable under different damping, initial condition and the amplitude of axial excitation are obtained. The conclusion show that both the natural frequency of cable and external parameter have directly influence on the number of stable solutions and their stability, the results can lead the design of cable parameter.