The one-dimensional momentum theory is essential for understating the physical mechanism behind the phenomena of the DAWT (Diffuser-Augmented Wind Turbines). The present work tries to extend the existing GADT (Generalized Actuator Disc Theory) that proposed by Jamieson (2008). Firstly, the GADT is modified to include an effective diffuser efficiency, which is affected by the thrust loading or axial induction. Secondly, Glauert corrections to the DAWT system in the turbulent wake state are proposed, modelled by a linear and a quadratic approximation, respectively. Finally, for prediction of the axial velocity profile at rotor plane bearing various thrust loadings, an empirical model is established, which can be further used to predict the diffuser axial induction. In addition, the 'cut-off point' in Glauert correction and the 'critical thrust loading' in axial velocity profile prediction are newly defined to assist the analysis. All the above formulations have been compared and validated with Jamieson's results and Hansen's CFD data, justifying the effectiveness of the present model. (C) 2015 Elsevier Ltd. All rights reserved.