In order to quickly calculate the content of DNMT in mixed explosives,the detection system for content is designed based on the terahertz (THz) reflective spectroscopy.In the system,stepper motor contr ols the movement of lens to obtain the large scanning range of the optical path ,and coherent effects are produced between echo reflected light irradiated on th e measured powder and local oscillator light.The content expression of DNMT is derived,and the filtering algorithm and extract requests are given for increasing the stability of reflective type detection method for DNMT.In the experiment,TeraTune type THz laser and DSTMS-1type THz detectors were used for data acquisition.Multiple sets of mixed samples with known DNMT content were tested by the system.Test results were compared with those of the TeraSys 4000type THz spectrum ana lyzer. Experimental results show that both methods quickly get samples DNMT content and test accuracy is better than 3.0%.When the pretreatment method of spectrum is used with more types in the sample mixture,i t still has good test results,with high anti-jamming capability.