In order to study combustion performance of the modified single base propellant composed of 5/7 single base propellant as base, NG as dipping reagent and polyester as coat regent, a theoretical analysis and an experimental validation for the dipping layer distribution in grain, the changes of grain size and energetic characteristic in combustion process have been studied. Two samples with 10% and 15% NG dipping quantity were prepared. Closed bomb test and micrograph observation of grain slices were done, and a calculation for the experimental results was carried out with the found model. Results show that the impetus of the sample containing 15% NG dipping reagent increases by 10.14%, and dipping depth is about 0.168 mm. The u-p curves of the single base propellant obtained by calculation is higher than that of the modified single base propellant before 150 MPa, and the u-p curves of both overlap with each other after 150 MPa. As long as the dipping reagent ratio of NG to polyester is appropriate, both impetus and progressive burning performance of the modified can get increasing within a certain range. Both impetus and progressive burning performance of the modified single base propellant can be increased within a certain range.