This paper represents a bistable optical device (BOD) using Ti-diffused LiNbO3 branched optical waveguide modulator which is fabricated in authors laboratory. The steady characteristic is analyzed and calculated theoretically. From the experimental results, half wave voltage Vx =9.0 V and maximum modulation depth= 46% are obtained. The calculated band width is about 5.5 GHz. The bistable hysteresis curves, critical curves, and the dull saturated curves are observed. They agreed well with the theoretical analyses and calculated results. The Improvements for this device are discussed.