A universal pulse width modulation method for a multi-level inverter includes the following steps: a, carrying out per unit of reference input voltages; b, calculating a two-level space vector pulse width modulation duty ratio; c, calculating in which layer a reference voltage vector is on; d, performing vector reverse mapping; e, inhibiting common-mode voltages; and f, generating pulse-width modulated waves. A voltage vector switching time duty ratio of an inverter is calculated by a simple two-level space voltage vector modulation algorithm, then vector compression is performed on the duty ratio, a mapping relation based on the voltage vector and level is established, and multi-level voltage conversion can be effectively achieved through the series of conversion. Through level conversion, the voltage vector that has a common-mode voltage inhibition capability can be output easily and quickly, and a specific pulse width modulation output state is selected to prevent generation of common-mode voltages, thereby effectively inhibiting common-mode components included in output voltages of a multi-level inverter.