Abstract: The principles and methods of tissue-equivalent proportional counter (TEPC) system were investigated. A set of measuring system based on TEPC was constructed, which was used to measure the absorbed dose and the dose equivalent in the neutron, gamma mixed field. There are always photons existing in the neutron field, so the micro-dosimetric spectra of mixed fields always include the two parts from photons and neutrons respectively. And the two parts can be simply separated according to their shapes. The micro-dosimetric spectra were obtained from the pulse height spectra, and the neutron and gamma components were analyzed. The simulation calculation was performed by Monte-Carlo method, whose result is in agreement with the measured data. Then, we know that the measurement of TEPC system is practicable.