Abstract: In view of the electromagnetic ultrasonic testing technology problems encountered in ferromagnetic materials,the paper studies the contribution of magnetostrictive effect on exciting acoustic field according to the constitutive equation of the magnetostrictive effect.In order to avoid the discussion of magnetostrictive force,the process of exciting acoustic field based on magnetostrictive effect is directly analyzed from the elastic displacement equation,which makes it unnecessary to calculate the body force of elastic particles.A specific EMAT structure model is simulated in Matlab to verify the correctness of the theory.The simulation analyzes the time-space curves of displacement equation to calculate the acoustic filed.The results match with those got by describing magnetostrictive effect with magnetostrictive force on related papers,which verifies the feasibility of the theory proposed.