An ultra-broadband silicon waveguide micro-electro-mechanical systems (MEMS) photonic switch is provided, which is mainly composed of three parts: input waveguides, a waveguide crossing with a nano-gap, and output waveguides. The waveguide crossing is composed of two identical orthogonal elliptical cylinders. Four ports of the waveguide crossing respectively extend to form single-mode strip waveguides to serve as input/output waveguides. The center of the waveguide crossing is fully etched with a nano-gap. The two symmetrical port waveguides are fully etched with nano-grooves. The lower cladding near the waveguide crossing and the nano-grooves is penetrated and etched. The width of the nano-gap is adjusted through adjusting a voltage applied across both ends of the waveguide crossing, so that a guided-mode directly passes through or is totally reflected. In the disclosure, a propagation path of the photonic switch is switched through adjusting the voltage applied to the waveguide crossing.