To improve the combustion performances of single-base propellant, GAP-base polyurethane was used as the coating material, the 4/7 single-base propellant was coated by using premixed-sprayed-cured technology. The effect of coating was observed by a three-dimensional video microscope. The compatibility of GAP-base polyurethane and single-base propellant was investigated by differential scanning calorimetry(DSC). The energies and combustion performances of coated single-base propellant were studied through theoretical calculation and closed-bomb test. The results show that the thickness of GAP-base polyurethane layer is relatively uniform, which has good adhesion and good compatibility with the single-base propellant. The introduction of GAP-base polyurethane makes the powder force and detonation temperature of gun propellant decrease, but the powder force is significantly lower than that of the inert polymer. GAP-base polyurethane coated single-base propellant has significant combustion progressivity, with increasing the coated amount, the progressivity gradually increases. Compared with the single-base propellant, the relative pressures at split point(B_s) of the GAP-base polyurethane coated single-base propellant with the coated amount of 7.05%, 9.67% and 11.88%, increases from 0.151 to 0.453, 0.480 and 0.489 respectively, and the values of the progression factor(P_r) increases from 0.090 to 0.293, 0.340 and 0.358, respectively.