The first gamma-ray total absorption facility composed of 40 BaF₂ detector units has been constructed in China. Utilizing the property of high detection efficiency and good time resolution for gamma rays of BaF₂ crystal, the facility will be used to measure on-line the cross section of neutron capture reaction. Neutron source of 250 keV～850 keV was set up on the HI-13 tandem accelerator, its source intensity at 0° was about 5.09 × 10⁶ n/(Sr·s). The experimental data of ⁹³Nb, ¹⁹⁷Au, ^natC and empty samples were measured by the prompt gamma ray method with gamma-ray total absorption facility. According to the characteristics of BaF₂ detector signal, a variety of digital waveform analysis methods were adopted to eliminate noise signal as much as possible to improve the effect background ratio, such as baseline compensation, software threshold setting, time window limitation, pulse amplitude integral growth rate setting and fast slow component ratio setting. The experimental data of ⁹³Nb neutron capture reaction cross section was obtained by relative measurement method. The data of ¹⁹⁷Au sample was the standard, the data of ^natC sample was the sample correlation background, and the data of empty sample was the sample independence background. The feasibility of the measurement facility and technical method was verified by comparing with the data of ENDF evaluation library.