The high speed orbit display capable of following one bunch during one turn was built for KEK 12 GeV proton synchroton and has been used during the present running in period. The information on the beam orbit and its variations during one turn is very helpful for a systematic tune up at the injection of the cycle and steering the beam on to target and ejection channels. In order to follow betatron amplitudes, 56 pick-up electrodes (28 horizontal, 28 vertical), 4 per betatron wave length, are distributed around the main ring of about 300 m circumference. The position signals obtained from pick-up electrodes are sent to two local control rooms via low loss coaxial cables. These signals are digitized by specially designed analogue-to-digital converter and then sent to the satellite computers upon request. The computers are connected to the KEK control computer network. The central computer collects the data from two satellite computers and calculates the beam position at each electrode and displays the results on graphic terminal. The system was intended to be economical, ease of maintenance and wide dynamic range with high accuracy. The overall accuracy of the position measurement, including electrode alignment, is expected to be 1more » mm +- 3% of the distance from center.« less