This paper used the method of distributive parameter's dynamic in[1]、[2] to calculate the phase-to-phase stress of conductive line in short circuit condition(i. e. dynamic stability). This method strictly according to the facts that conductive line as a thin beam, it's quality elasticity, resistance all was distribution. Therefore, it could depite the dynamic feature of conductive line more precisely In[3] one considered many step、elastic constrain、inner-resistance (inner friction of Aluminium material)、extra-resistance (atmospheric resistance) e. t.al. This paper considers a horizontal stress based on[3], may calculate stress of dynamic state and inverse stress of dynamic state of fulcrum.The mathematical problem, which was depicting above physical problem, was a partial differential equation of parabolic type in five orders. This paper get a numerical solution that could use difference method. Numerical results shows:when the conductive line in short circuit condition was increasing a little horizontal stress, (constract with other quatity), the numerical results only has a little shift.This paper also analyze the computational stability condition of explicit difference schme. It's results shows:when increasing a horizontal stress, the computational stability condition as same as before.