Aiming at the problems of traditional photovoltaic grid-connected system structure， a new type of photovoltaic grid-connected cascaded inverter scheme with stepped waveforms and instantaneous value feedback hybrid control. In this method， one part of the cascaded units use stepped waveforms control， the other part use octave sinusoidal pulse width modulation（SPWM） control with instantaneous current feedback. The output voltage comes from the two parts in series. The analysis of the output voltage harmonic shows that the amplitude of the output voltage and the power factor can be adjusted by the SPWM wave phase-shift angles; the low order harmonic of the output voltage is aroused by the stepped waveforms control part， which is the theoretic background for the output filter design. A simple algorithm for the trigger angles of the stepped waveforms modulated inverter is proposed， which is not only fit for the cascaded inverter with different voltage steps， but also fit for online calculation. The experimental results show that this scheme has simple structure， high reliability and low switching loss.