When the high voltage breaker acts, the contacts can form an arc, and be accompanied by evaporation and splash phenomenon, which causes the material erosion and contact system invalid. In order to study the characteristics of the splash mechanism of the ablation failure of high voltage circuit breaker, the flow and heat transfer models of the arc bath were established. And the temperature, flow and pressure distribution of the contact in the different arc root were analyzed by using FLUENT. The results show that: Under the two arc root conditions, a semicircle molten pool is formed. And at the condition of small arc root, the energy is not conducive to the distribution of energy and arc movement, resulting in a larger flow rate, increasing the erosion of the electrode. The flow rate of the molten pool increases with the current, and the greater the current is, the faster the velocity of fluid in the arc root zone rises from the minimum to the maximum, and the melting speed of the molten pool is also accelerated.