In the area of molecular magnetism,single molecule magnets (SMMs) containing lanthanide elements are of immense scientific and technological interest because of their large energy barriers and high measured hysteresis temperature.Although there has been significant progress in the synthesis and characterization of lanthanide-based SMMs,there are still challenges,for instance,how single-ion anisotropy of lanthanide elements can be exploited,and how zero-field tunneling of magnetization can be suppressed.This article is devoted to the progress in various methodologies for modulating magnetic relaxation,especially in terms of crystal field and magnetic interactions.The crystal field plays a dominant role in creating single-molecule magnets with largely anisotropic f-elements,while the strong coupling between magnetic centers is able to suppress quantum tunneling of magnetization efficiently. In the area of ​​molecular magnetism, single molecule magnets (SMMs) containing lanthanide elements are of immense scientific and technological interest because of their large energy barriers and high measured hysteresis temperatures. There has been significant progress in the synthesis and characterization of lanthanide-based SMMs, there are still challenges, for instance, how single-anisotropy of lanthanide elements can be exploited, and how zero-field tunneling of magnetization can be suppressed. This article is devoted to the progress in various methodologies for modulating magnetic relaxation, especially in terms of crystal field and magnetic interactions. The crystal field plays a dominant role in creating single-molecule magnets with indispensable anisotropic f-elements, while the strong coupling between magnetic centers able to suppress quantum tunneling of magnetization efficiently.