In order to synthesize high-purity 3，5-diamino-2，4，6-trinitrochlorobenzene （DATNCB）， the synthesis route screening and process optimization of DATNCB were studied with 1，3，5-trichloro-2，4，6-trinitrobenzene （TCTNB） or picric acid （2） as raw materials， respectively. The structure of the product was characterized by IR， NMR and MS； the thermal behavior of DATNCB was studied by DSC-TG； the purity of DATNCB was analyzed by HPLC. The results show that： the best synthetic route of DATNCB is starting from picric acid， then by via VNS amination followed by chlorination. The total yield is 39.2%. The highest yield of 3，5-diamino-2，4，6-trinitrophenol （3） was 74.8% when VNS amination temperature was 90 ℃ and post-treatment pH value was 3； the highest yield of DATNCB was 52.4% when phosphorus oxychloride/N，N-dimethylaniline was used as the chlorination reagent， the reaction temperature was 80 ℃ and the reaction time was 10 h. The melting point of DATNCB is 224.0 ℃. There is only one weight loss stage in the range of 179.7-270.9 ℃ and the weight loss rate is 91.6%； the peak decomposition temperature is 256.1 ℃. The purity of DATNCB reach 97.09% without further purification， and up to 99.8% after recrystallization with ethyl acetate/petroleum.