A tunable Si photonic nano-wire (320nm-wide, 340nm-thick) waveguide micro-ring resonator composed of triply-linked variable couplers (two are for wavelength tuning and one is for bus-line coupling) is proposed. The roundtrip optical path of the micro-ring is modulated by the displacement of coupler waveguide with an ultra-small comb-drive actuator. In addition, the coupling between the micro-ring and a bus-line waveguide is also controlled by a gap-variable waveguide coupler with another actuator. Therefore, the proposed tunable micro-ring can be operated as an ultra-small wavelength-selective-switch with a wavelength-hitless mechanism for Si on-chip telecommunication system. Principle, design and fabrication are presented. The characteristics of the proposed device are measured in 1.5μm fiber optic telecommunication wavelength region. The wavelength tuning range is 10.0nm for the actuator displacement of 1.0μm at the voltage of 37.3V.