We present an integrated SOI optical microswitch, composed of silicon waveguides and electrostatically actuated gold-coated silicon micromirrors. The optical microswitch serves as an optical signal transceiver containing an LD receiver and a PD transmitter. For lower micromirror switching voltage, we modify the conventional curved electrode microactuator into the new microactuator with touchdown beams. In addition, we simplify the structure and the process of the microswitch by using the ICP etching of SOI wafers. From the fabricated microswitch, we measure the switching voltage of 31.7±4V at the resonant frequency of 6.89kHz. Compared to the conventional microactuator, the touch-down beam microactuator achieves 87.4% reduction of the switching voltage. We observe the single mode wave propagation through the silicon waveguide with the measured micromirror loss of 4.18±0.25dB. We analyze major source of the micromirror loss, thereby presenting design guidelines for low-loss micromirror switches. We discuss a feasible method to reduce the switching voltage to 10V by reducing the residual stress of electrode insulation layer to 30MPa.