In this paper, a simple consititutive parameter identification method for the application of domain model in Tb0.3Dy0.7Fe2 alloy is studied, the magnetization and hystersis characteristics are summarized. Targeting the problem of unclarity and difficulty in directly testing the constitutive parameters in Tb0.3Dy0.7Fe2 alloy, numerical calculation and experimental test are used to propose a parameter identification method. Coordinate transformation and graphic solution technique are used in this paper to simplify the minimization solutions of domain rotation in alloy. The dependence of parameters in magnetic rotation model is studied. On this basis, combined with simple experimental test, the method of indentifying Tb0.3Dy0.7Fe2 alloy is established, and the influences of anisotropy constants K1 and K2, energy distribution factor ω, axis orientation distribution in domain rotation are discussed. The method can simply and rapidly identify the constitutive parameters of Tb0.3Dy0.7Fe2 alloy in magnetic domain model, which is significant to improve the numerical calculation of domain rotation in magnetostrictive material. The above theoretical computations are significant for establishing magnetomechanical model of magnetostrictive material, and results are helpful for perfecting the identification of constitutive parameters.