We present a complete surface-potential-based compact model of dynamically depleted (DD) SOI MOS-FETs. The surface potential equation of DD-SOI MOSFETs was reconditioned to avoid the unphysical behaviors near the fiat-band voltage. In order to capture the dynamic depletion effect, the coupling equation for the front and back surface potentials was reformulated to include the back gate effect, which is not available in other surface-potential-based DD-SOI compact models. The new formulation of surface potential and coupling equations was verified by comparing with numerical computations combining the Pao-Sah double integral based formulation and the exact coupling equation. To obtain explicit expressions for the terminal charges and drain current, a new symmetric linearization method has been proposed. The complete model, PSP-SOI DD is implemented in the context of the PSP and PSP-SOI PD models and includes all the secondary effects, floating body simulation capability, etc. The new model has been extensively verified with 2D TCAD simulation results and accurately captures the manifestation of the dynamic depletion effect observed in the device characteristics. Published by Elsevier Ltd.