A novel design and fabrication approach for a high fill-factor micro-electro-mechanical system (MEMS) micromirror array-based wavelength-selective switch (WSS) is presented. The WSS is composed of a polarization-independent transmission grating and a high fill-factor micromirror array. The WSS is successfully demonstrated based on the fabricated high fill-factor micromirror array. Test results show that the polarization-dependent loss (PDL) is less than 0.3 dB and that the insertion loss (IL) of the wavelength channel is about –6 dB. The switching function between the two output ports of WSS is measured. The forward switching time is recorded to be about 0.5 ms, whereas the backward switching time is about 7 ms.