Abstract: Radioactive xenon in the atmosphere is one of important components for international monitoring system (IMS) of comprehensive nuclear-test-ban treaty (CTBT). To improve the detection sensitivity and measurement accuracy of radioactive xenon isotopes is the forefront of CTBT research. In the work, a type of β detector made of Si-PIN semiconductor for measuring radioactive gas xenon isotopes was developed. The electron energy resolution of the Si-PIN β detector is about 11.2% (129 keV ¹³¹Xe^m) and far superior to the electron energy resolution of the plastic scintillator. The xenon memory effect of the Si-PIN β detector is only 0.08%. So the excellent performance of the Si-PIN β detector will improve the identification ability and measurement accuracy of the xenon sample analysis.