The embodiment of the invention provides a driving method used for a diode clamping type three-level bridge arm and a bridge arm logic unit. The driving method comprises the following steps: carrying out following processing under a stable processing state: obtaining a current input driving signal; comparing the current input driving signal with an output driving signal of the former period; if the current input driving signal is different from the output driving signal of the former period, judging whether the quantity of open electric level signals in the current input driving signal is more than that of open electric level signals in the output driving signal of the former period or not; if so, entering a dead-zone processing state and carrying out the following processing: waiting for pre-set dead-zone time and entering an open processing state; carrying out the following processing: selecting an IGBT (Insulated Gate Bipolar Translator) needing to be opened according to the current input driving signal, and changing a corresponding phase change in the output driving signal of the former period into an open level signal; and waiting for pre-set first bandwidth pulse inhibiting time and entering the stable processing state.