An analytical model on threshold voltage and subthreshold swing for high-k gate dielectric GeOI MOSFET (metal-oxide-semiconductor field-effect transistor) is established by considering the two-dimensional effects in both channel and buried-oxide layers and solving two-dimensional Poisson’s equation. The influences of the main structural parameters of the device on threshold voltage and subthreshold swing, and the short-channel effects, drain induction barrier lower effect and substrate-biased effect are investigated using the model, and the design principles and value range of the structural parameters are presented to optimize the electrical performances of the device. The simulated results are in good agreement with the TCAD simulated data, confirming the validity of the model.