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Diamond has superior physical and electronic properties and it is regarded as an ultimate material of power-electronics applications. Numerous studies have been focusing on the diamond-based power devices, especially on diamond metal-oxide-semiconductor field-effect transistors (MOSFETs). Due to the existence of two-dimensional hole gas (2DHG) layer on the hydrogen-terminated (H-) diamond surface, hole carriers with high density can be provided and thus H-diamond MOSFETs have been widely investigated, whereas they generally exhibit normally on properties. In recent years, many researchers have been devoting themselves to the development of diamond MOSFETs with normally off characteristics and good device performances. In this work, we summarized recent advances to achieve normally off features for diamond MOSFETs, including the partial surface modification or using some specific insulator materials on H-diamond surfaces, the oxidation of the silicon terminated (Si-) diamond, and the inversion-type p-channel diamond MOSFETs on hydroxyl terminated (OH-) diamond. In addition, we summarized their interface properties which mainly limited the device performances, and put forward to the possible approaches to improve the device performances and thus to promote their potential for power application.