Abstract: For neutron scattering spectrometer, performance parameters of each detector system component need to be adjusted. Accurate determination methods can improve practical performances of detector system and experimental data quality(credibility). Based on neutron scattering spectrometer detector system with ³He proportional counting tube, pulse amplitude spectrum determination methods for discrimination level determination and demarcating detector operating voltage and gas amplification curve of gas radiation detector were developed. Compared with traditional determination methods (integral curve, plateau curve and voltage-current curve), the new determination methods have many advantages such as short measuring time, high accuracy and wide application area.