Lai, L.W. Chen, Z.C. Leng, Y.B. Yan, Y.B. Yu, L.Y. Yuan, R.X. Zhou, W.M. JACoW Geneva, Switzerland 978-3-95450-176-2 10.18429/JACoW-IBIC2015-TUPB036 English 399-401 TUPB036 cavity electronics FEL electron diagnostics Contribution to a conference proceedings 2016 2016-01 http://dx.doi.org/10.18429/JACoW-IBIC2015-TUPB036 http://accelconf.web.cern.ch/AccelConf/IBIC2015/papers/tupb036.pdf Shanghai Soft X-ray FEL Test Facility (SXFEL) has started the infrastructure construction in 2015. All beam diagnostic systems are under processing and measurement, including C-band Low-Q cavity BPMs. This paper presents the progress of the cavity BPM system, including design and the measurements on a lab platform. Measurements shown that the cavity BPM frequency is 4.7GHz±8MHz, and the complete test platform verify that the cavity BPM system, which including signal processing electronics can work as expected.