A high performance liquid chromatography (HPLC) method was developed for the separation of 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) and 1,3,5-triacetyl-1,3,5-triazacyclohexane (TRAT), which are the intermediates for the synthetic reaction of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX). The chromatograms of TAT and TRAT were further confirmed by high performance liquid chromatography-mass spectrometry (HPLC-MS). The optimal separation conditions are: sillca column (4.6 mm×250 mm i.d., 5 μm), mobile phase: acetonitrile/water (75/25, V/V); the flow rate is 1.0 mL·min^-1, the wavelength is 215 nm, the injection volume is 20 μL.