The combustion characteristics of the high-energy smokeless modified double-base propellant (HESMDB) at 10-43 MPa was studied. Results show that the burning rate of HESMDB increases with pressure enhancement. There is an inflexion point in the combustion curve of HESMDB propellant at 25 MPa, and then the burning rate of HESMDB increases rapidly. The effects of combustion catalyst is obvious on HESMDB at 10-25 MPa, and lessened at 25-43 MPa. NI-Pb/NI-Cu/CB enhances the burning rate of HESMDB 75.16% at 10 MPa.