Abstract: In view of the high cost and sparse spatial resolution of the offshore meteorological observation, wind maps retrieved from the satellite synthetic aperture radar (SAR) data are valuable in offshore wind energy planning as a supplement to on site measurements, which is crucial in offshore wind resource assessment. The advanced SAR maps monitored by Envisat in 2002 have been widely used in off-shore wind resource assessment in Europe. The technical methods of off-shore wind resources assessment at Hangzhou Bay based on the near 1 km×1 km SAR wind retrieval data are investigated. Comparison of the in situ wind speeds at Hangzhou Bay and the SAR wind retrieval shows that (1) the relative errors of most off-shore observation stations (13/14) are less than 20%, of which 7 stations less than 10%, and the standard deviation is 2.29 m/s; (2) high consistency has been found on the wind energy parameters (shape parameter and scale parameter) calculated by the SAR wind retrieval and the in situ wind; (3) compared with the control experiment, when the SAR wind retrieval assimilated into the numerical model (WRF), it shows a significant improvement on the wind speed correlation coefficient at most of the observation stations and some decrease in standard deviation as well as relative error, suggesting that high resolution SAR wind retrieval is able to be applied to offshore wind resource assessment in China.