A diagram for the dependence of the composition on temperature (TX-phase diagram) for the ternary system has been constructed by calculating from the data of three binary systems on the basis of certain assumptions. Two sets of equations for the liquidus line of the eutectic compositions and temperatures. The TX-phase diagrams, i.e. the temperature dependence on composition, of four ternary systems of the energetic materials, including AK/EDD/NQ, AK/EDD/NTO, Tetryl/PETN/RDX and TNB/Tetryl/PETN, were constructed. It is shown that the errors for the calculation of the eutectic composition and temperature are within +/-2.0 mol% and +/-2 degrees C respectively.