High purity 2，4，6-trinitro-5-ethoxy-1，3-phenylenediamine （DATNEB） can be used as an internal standard in high performance liquid chromatography （HPLC） to accurately analyze the purity of TATB synthesized by the chlorine-containing method. To study the synthesis and energetic properties of DATNEB， high purity DATNEB was prepared from picric acid by aminating with 4-amino-1，2，4-triazole （ATA） and then ethylating with triethyl orthoformate. The overall yield was 32.5% and the purity was over 99.8%. The structure of the product was characterized by IR， ¹H NMR， ¹³C NMR， MS and X-ray single crystal diffraction. The mechanisms of amination and ethylation were discussed， the thermal and detonation properties of DATNEB were also studied. The results show that DATNEB crystallizes in a monoclinic system， space group P2₁/c with a=1.21261（7） nm， b=0.89654（4） nm， c=1.12310（6） nm， V=1.17675（11） nm³， Z=4， ρ=1.62 g·cm^-3. DATNEB exhibits an endothermic peak at 193.9 ℃ and exothermic peak at 236.0 ℃， indicating a good thermal stability. It has a detonation velocity of 7.05 km·s^-1 and detonation pressure of 21.14 GPa，which is comparable to TNT， while the sensitivityis much lower than that of TNT and RDX. Therefore， the synthesized high-purity DATNEB can not only be used as an internal standard， but also an auxiliary component of molten-cast explosives.