The effects of the content of Hexogen（RDX）and Nitroguanidine (NGu) on the combustion behavior of nitramine propellants under low pressure were studied in the closed bomb. The combustion data of six kind of nitramine propellants with different ratio of RDX /NGu were obtained from 20 MPa to 60 MPa by the closed bomb test. The results indicate that there is a change of burning rate pressure exponential of nitramine propellants,and the content of NGu can adjust the combustion rules of nitramine propellants under low pressure.