<正>The beam phase measurement is a key for obtaining an optimization of isochronous magnetic field in accelerator, to improve the beam quality and increase the beam intensity and efficiency of the beam extracted from accelerator. The 15 sets of the capacitive pick-up pha.se probes were mounted at equal distances above and below the median plane of the SSC.The size of the plate is 100×100 mm and the distance between two plates is 40 mm. The high frequency mixer and filter technology is used to develop the beam