The impacts of remote Coulomb scattering (RCS) on hole mobility in ultra-thin body silicon-on-insulator (UTB SOI) p-MOSFETs at cryogenic temperatures are investigated. The physical models including phonon scattering, surface roughness scattering, and remote Coulomb scatterings are considered, and the results are verified by the experimental results at different temperatures for both bulk (from 300 K to 30 K) and UTB SOI (300 K and 25 K) p-MOSFETs. The impacts of the interfacial trap charges at both front and bottom interfaces on the hole mobility are mainly evaluated for the UTB SOI p-MOSFETs at liquid helium temperature (4.2 K). The results reveal that as the temperature decreases, the RCS due to the interfacial trap charges plays an important role in the hole mobility.