OH incorporated in nominally anhydrous minerals (NAMs) has received increasing attention due to its profound influence on the chemical and physical properties of minerals. Olivine is the most abundant mineral phase in the upper mantle, and a trace amount of water in its structure would lead to a large effect on the rheology and conductivity of the upper mantle. Thus, the knowledge of the mechanisms of H incorporation in olivine's structure and the mechanisms and rate of H diffusion in its lattice is helpful to understand the water circulation between the surface and the deep earth and to explain the rhelogically and magnetotellurically observed data. In this paper, the authors compiled studies of olivine during the last two past decades on how H associated with different point defects correlate with the apparent infrared absorption bands, how these different H diffuse through the lattice and how fast these diffusive fluxes occur. The problems existent in these researches are also pointed out in this paper.