The incorporation of nano-scaled cyclotrimethylene trinitramine (nRDX) in nitrocellulose (NC)-based propellants poses processing problems when following conventional methods. Hence, a new preparation method containing a pre-dispersion process was developed, by which 30mass% RDX (290nm) was incorporated in the propellant. Meanwhile, the corresponding 290nm, 12.85m and 97.76m RDX-based propellants were prepared for comparison using a conventional method. The morphology, structure, ballistic and mechanical properties of the prepared propellants were characterized by scanning electron microscopy (SEM), density analyzer, closed vessel (CV), uniaxial tensile tester and impact tester. The results indicate that the nRDX particles were uniformly dispersed in the NC/NG/TEGDN matrix using the novel method, while agglomerated and recrystallized into large particles with the conventional method. The propellant density increased with decreasing RDX particle size. In particular, the 290nm RDX-based propellant exhibited a higher burning rate and lower average pressure exponent (=0.958) compared to the 12.85m RDX-based propellant (=1.043). The tensile strength, elongation at break and impact strength of the RDX-based propellant at -40 degrees C, 20 degrees C and 50 degrees C were dramatically improved by using 290nm RDX with the novel method.