In this paper, we report a MEMS-variable attenuator (VOA) with unique SOI based electrostatic torsion mirror structure to realize simple fabrication process and low voltage, stable operation, as well as high production yield. In the proposed device, attenuation principle is a simple beam deflection method by using tilt mirror, which deflects the incoming optical beam, and thus changes coupling loss at the output fiber end with respect to the beam mode profile. The whole MEMS structure is made of silicon-on-insulator (SOI) wafer, where a shaped through-hole made by deep RIE (DRIE) under the half side of the rotational mirror suspended by torsion bars automatically defines the electrode on the opposite side with respect to the upper device silicon layer. A number of careful design tips are taken into account for high temperature stability and anti-shock/vibration performance. Fabrication process of the chip is also as simple as it is designed so that it only requires two DRIE processes and three photolithography steps. For the finished pigtail module, dual fiber with an aspherical collimator lens, and a CAN package with MEMS chip mounted inside are tightly welded by YAG laser in order to ensures both environmental reliability and operational stability. Driving voltage as low as 5V provides attenuation range over 45dB while maintaining anti-shock/vibration characteristics. Selective deposition of metal layer coating on the circular mirror section suppresses temperature dependent fluctuation less than 0.5dB at 20dB attenuation over 0 to 70degC range by decoupling bimorph effect of metal layer from the electrostatic operation.