The invention provides a quick electromagnetic transient simulation method and device for a modular multi-level converter. At least one valve section in each bridge arm of the modular multi-level converter is equivalent to a valve section equivalent circuit; the valve section equivalent circuit comprises a first diode, a second diode, a first controlled voltage source, a second controlled voltage source and a third controlled voltage source; the common end, where the anode of the first diode is connected with the cathode of the second diode, is used as the positive end of the valve section equivalent circuit; the cathode of the first diode is connected with the anode of the first controlled voltage source; the anode of the second diode is connected with the anode of the second controlled voltage source; the common end, where the cathode of the first controlled voltage source, the cathode of the second controlled voltage source and the anode of the third controlled voltage source are connected, is used as the midpoint of the valve section equivalent circuit; and the cathode of the third controlled voltage source is used as the negative end of the valve section equivalent circuit. The valve section equivalent circuit obtained through the method and the device has good universality.