In this digest, we propose a new staircase matrix modulation (SMM) for the switched-capacitor modular multilevel converter (SCMMC). SMM is a low-frequency modulation technique, achieving sensor-less capacitor voltage balancing with a staircase output voltage. The new SMM is derived from Y-matrix modulation (YMM), but it solves the voltage unbalancing issue caused by applying YMM at low PWM frequencies. To achieve voltage balancing at fundamental PWM frequency and synthesize a staircase output voltage, the proposed SMM uses: 1) a modified switching pattern rotation scheme compared to YMM and 2) a new switching matrix 𝐂 with a unique symmetry feature.