A design of micromachining based direct-coupled variable optical attenuator (VOA) is presented. The device operates by misaligning a fiber-to-fiber coupling through a lateral displacement of one of the fibers mounted on a micro-machined flexure driven electromagnetically. The VOA was fabricated using CNC engraving and laser spot welding technologies and features a fast dynamic response (<2.3 ms), great dynamic range (0～65 dB) and wide bandwidth. In order to optimize micro-mechanical structure an FET software package ANSYS was employed and simulation of the device operation is reported in details.