An analytical model for drain current of high-k gate dielectric fully-depleted nanoscale germanium-on-insulator (GeOI) p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) is established by solving two-dimensional Poisson's equation to derive the surface potential and inversion charge in the channel region. This drain current model includes velocity-saturation, channel-length modulation and mobility-modulation effects; and it simultaneously considers the impacts of the interface-trapped charges at both gate oxide/channel and buried oxide/channel interfaces and the fixed oxide charges on the drain current. A good agreement between the simulated drain current and experimental data is achieved in both the saturation and non-saturation regions, confirming the validity of the model. Using the model, the influences of the main structural and physical parameters on transconductance, output conductance, cut-off frequency, and voltage gain of the device are investigated. These can be served as a guide for the design of the GeOI PMOSFET.