In order to study the effects of RDX on the safety performance of nitramine modified double base propellants(MDBP), detonator sensitivity test, shock sensitivity test, detonation safety test and detonation velocity test were carried out respectively according to GB14372-1993 and GJB772A-1997 for nitramine modified MDBP samples with different content of RDX(18.0%~55.1%) and a common MDBP sample. Results show that with increasing of RDX content, the propellant has higher sensitivity to shock wave and detonator, lower detonation safety, and its detonation velocity of propellant increases. Detonator could explode the propellant at -5 ℃directly when the content of RDX in propellant is 34%. The critical gap thickness is up to 33.5 mm, the propagation critical diameter of detonation 8 mm and the detonation velocity more than 8000 m·s^-1 when the content of RDX is 55.1%.