A novel variable optical attenuator based on micro-electromechanical system is reported. The variable optical attenuator employs a low-cost simple structure design, capable of fast dynamic response (<2 ms), wide dynamic range (0～35 dB), low return loss (<-50 dB) and wide bandwidth. By utilizing precise electrical-discharge machining as an enabling technology, the design incorporates an electro-magnetically actuated silicon mirror rotating around a 100 m shaft and a miniature driven coil. The attenuation response is compared with the calculated result from a numerical theoretical model by using ANSYS, a finite element analysis software package, and a reasonably good agreement was obtained. The variable optical attenuator is scalable to a discrete array to implement dense wavelength division multiplexing channel equalization in various networking devices.