In the actual neutral point clamped three-level inverter circuit, switching sequence more than 8 segments is often used in order to control the neutral-point voltage unbalance, but it is hard to implement actually. By injecting a specific zero sequence component into the modulation wave, carrier-based pulse width modulation would be equivalent to space vector pulse width modulation. So far, seldom research about the equivalence between carrier-based pulse width modulation and space vector pulse width modulation with a switching sequence more than 8 segments was done. Based on double modulation wave pulse width modulation theory, this paper demonstrates the equivalence between carrier-based pulse width modulation and space vector pulse width modulation for a three-level inverter. By mathematical deduction, the relationships between the six sub-modulation waves and the original three-phase modulation waves as well as the DC voltages are derived whichever area or sector the reference vector locates in. The experiment results prove the equivalence.