Abstract: Accurate evaluation of the generation loss caused by wind turbine wake is an important part of wind farm design. Based on Gaussian wake model and momentum conservation,the effective wind speed deficit is introduced to calculate wind speed deficit in the impeller of wind turbine. Using the SCADA data of an offshore wind farm in China,the verification and analysis are carried out from radial and axial wake loss distribution. The results show that the wake distribution simulated by the Gaussian effective wind speed deficit method is more consistent with the measured wake loss law. The correlation coefficient between the radial and axial wake simulation results and the measured results exceeds 0.92,and the accuracy of effective wind speed deficit method is improved by 30%～40% compared with the impeller center wind speed deficit method. Compared with the Jensen and Frandsen models,the Gaussian effective wind speed deficit model is more stable. The effective wind speed deficit method improves the calculation accuracy of Gaussian model and makes it more suitable for wind farm power generation.