In the process of fitting the constitutive equations, the Bagley correction method was brought in to obtain the correction parameters to refit the constitutive equation and reduce experimental errors caused by the viscosity of paste propellant. The experimental errors were reduced from 8% to less than 2% by using the Bagley correction method. The obtained curve of the constitutive equations were consistent with the experimental data. The results showed that the Bagley correction method had an obvious effect in improving the accuracy of the equation to a certain extent.