The rapid development of additive manufacturing technology provides an effective way for the flexibility and adaptability of traditional solid propellant casting molding， however， to meet the requirements of the casting， the thermosetting solid propellants with good fluidity could not deposite layer by layer. In order to realize the additive manufacturing， the hydroxyl-terminated polybutadiene （HTPB） was modified by adding a small amount of styling aids. The rheological properties of the modified-HTPB and slurry made by using the modified-HTPB were studied. The rheological curve test results show that apparent viscosity and viscous flow activation energy of the modified-HTPB increase significantly with the decrease of temperature. The rheological property of the modified-HTPB solid propellant slurry is consistent with Herschel-Bulkley equation， and the fluidity of modified-HTPB solid propellant slurry increases with the increment of temperature. Besides， the slurry possesses high storage modulus（G′＞10⁴ Pa） and small loss tangent（ω＜10 rad·s^-1，G″/G′＜0.5） at ambient temperature， showing a low fluidity. A small amount of styling aids has little effect on the thermal decomposition behavior of the propellant， which promotes the 3D printing of the modified-HTPB solid propellant .