A method for establishing a constitutive relation of a class-II cement-based grouting material comprises the following steps: step 1, a group of homogeneous cement slurry is prepared from the class-IIcement-based grouting material; step 2, the cement slurry in step 1 is subjected to fluidity tests, and fluidity test data of the cement slurry is obtained; step 3, corresponding Euler-Euler model isestablished; step 4, at least three cement slurry models with different viscosity coefficients are set in the Euler-Euler model, then fluidity test simulation is performed on the cement slurry modelsuntil the difference between fluidity test data of one cement slurry model and the fluidity test data of the cement slurry in step 2 is smaller than 0.1 s, and at the moment, the viscosity coefficient of the cement slurry model is the viscosity coefficient of the cement slurry in step 1. The technical problem that establishment for the constitutive relation of the class-II cement-based grouting material as a mixed material is quite complicated is solved.