High performance liquid chromatography (HPLC) was employed to analysis the solubility of RDX in melting DNAN/MNA at the range of 87 ℃ to 95.3 ℃. The optimal chromatography conditions were as following: mobile phase is methanol/water=6/4 (V/V), and flow rate 1.0 mL·min^-1, and wavelength of detector 254 nm, and injection volume 5.0 μL. The influence of particle size, equilibration time and temperature programming on solubility was studied. Under the optimum condition, the curve of the solubility of RDX in DNAN/MNA as a function of temperature was built. Results show that the solubility of RDX increases with increasing of the temperature.