To determine the purity of 1，3-dichloro-2，4，6-trinitrobenzene （DCTNB） product accurately， a high-performance liquid chromatography （HPLC） real-time （or in-situ）method for the determination of DCTNB and its impurities， 1，5-dichloro-2，4-dinitrobenzene （DCDNB） and 2，3，4-trichloro-1，5-dinitrobenzene （TCDNB） was established.. The effect of different mobile phase system， mobile phase ratio， flow rate and injection volume etc. conditions on the separation of high performance liquid chromatography for DCTNB was discussed. The quantitative analysis method was carried out by an external standard method. Results show that The optimal chromatographic conditions obtained are as follows： hypersil ODS2 chromatographic column （250 mm×4.6 mm， 5 μm）， UV detection wavelength 240 nm， acetonitrile /water with a volume ratio of 55∶45 as mobile phase， flow rate 1.2 mL·min^-1， column temperature 25 ℃， injection volume 10 μL. Under the above chromatographic conditions， the retention times of DCDNB， DCTNB and TCDNB are 9.20， 10.50， and 14.17 min in sequence with good resolution of all peaks（greater than 3.70）. DCDNB， DCTNB and TCDNB show a good linear relationships in the concentration ranges of 5-250， 5-500 and 5-250 mg·L^-1， respectively， and the linear correlation coefficient R² is greater than 0.999. The detection limits of DCDNB， DCTNB and TCDNB are 0.47， 0.68， 0.85 mg·L^-1， the quantification limits are 1.58， 2.28， 2.82 mg·L^-1， respectively， the relative standard deviation of 1.01%-1.27%， and the standard recovery rates are 98.82%-102.13%．