The DC voltage divider is the core measurement equipment of the pole-bus voltage or the neutral-bus voltage. The correct measurement of DC voltage is the key to ensure proper control and protection actions. Actual operating experience has shown that the voltage transfer function has changed when there is internal flashover， which changes the resistance and capacitance values. Then the measured DC voltage at secondary side will be distorted， which leads to the misoperation of the DC control and protection system. Combining the measured waves， the DC voltage divider is modeled in PSCAD/EMTDC， and the flashover fault is simulated and analyzed. Some anti-accident measures are also provided to avoid such fault.