Abstract: The topology optimization structure obtained by the SIMP(solid isotropic material with penaliza-tion)method or RAMP(rational approximation of material properties)method has a large number of gray ele-ments,and the existing Heaviside function has the problem of calling the density matrix frequently,so the computational efficiency is relatively low.Aiming at this problem,an improved topology optimization method for suppressing gray elements is proposed in this paper.Firstly,a topology optimization model with minimizing the structural compliance as design objective is established;then,the Young's modulus is calculated by the SIMP method or RAMP method;finally,gray element is suppressed by the Heaviside projection function,and the topology optimization problem is solved by the OC(optimality criteria)method.The numerical simulation results show that:the two Heaviside projection functions proposed in this paper can suppress gray elements stably and effectively,and they can notably improve the definition and stiffness of the structure obtained by the SIMP method and RAMP method respectively.