The arc fault can release high energy, which poses great harm to surrounding objects and wires within a certain distance, and the generated heat can even cause a fire. First of all, the arc energy distribution and its damage to the pipe are analyzed in theory, and the real-time heat exchange between fluid and solid is simulated by the fluid-solid thermal coupled method. Finite element model is obtained, the arc damage is numerically simulated and the equation of arc energy distribution is obtained. The arc damage under the source voltage of DC28 V and AC115 V is studied and the prediction capability of the equation is verified. The simulation results show that: The arc fault can make the metal have phase transformation; The arc damage has a close relationship with the heat dissipation factor and the fraction of arc power， et al; When the arc power increases, the ratio of the energy used for phase transformation to the arc energy increases; The fraction of arc power is an exponential function related to the distance between the arc and the pipe.