To improve the mechanical property of single-based propellant with high nitrogen content, nitrocellulose/2,4-dinitrotoluen/diphenylamine(NC/DNT/DPA), 3% dimethylsulfoxide(DMSO), N,N-dimethylformamide(DMF), cyclohexanone, cyclohexane, chloromethane, ethyl acetateandbutyl acetate were added to alcohol ketone respectively to form ternary mixed solvent, plasticizing high-nitrogen nitrocellulose and obtaining the corresponding single-based propellant. The microstructure of single-based propellant samples were observed by scanning electron microscopy, and the mechanical properties were tested by universal material testing machine and beam impact testing machine. In addition,the energy of single-based propellant samples were studied by closed bomb test. Results show that when the auxiliary solvents are added, the mechanical properties of the high-nitrogen single-based propellant samples are improved. The compressive strength of the sample with 3% butyl acetate at low temperature (-40 ℃), normal temperature (20 ℃) and high temperature (50 ℃) increases by 15.7%, 4.3% and 17.7%, and the impact strength increases by 26.9%, 96.9% and 170.0%, respectively. The addition of the auxiliary solvent has little effect on the combustion of single-based propellant. And compared with the basic single-based propellant, the gunpowder force of the single-based propellant samples prepared by the ternary mixed solvent has a small decrease.