Based on stational observations and retrieved sea fog products by the Kuihua-8 satellite from January to June 2020, this paper have evaluated the performance of the independent researched and developed GRAPES-TYM model to forecast sea fogs over the Eastern China Seas. Results indicate that sea fog forecasting for the Eastern China Seas by GRAPES-TYM is relatively promising, for TS of 48 h and 72 h is 0.40 and 0.36, respectively. Especially the model shows the best ability to predict the Yellow Sea sea fogs with TS of most stations in the sea area between 34°N and 37°N higher than 0.50. The further assessment indicates that the fog area forecast under the uniformed pressure field is more accurate, with an average CSI of 0.35. The model often gives false alarms when under the back of the cyclone. It appears that deviations between observed and forecasted surface air temperature and relative humidity are relative to locality. The hit rate and TS are lower with underestimating relative humidity, and vice versa. Our results also suggest that for successful cases, the model accurately captures the near-surface meteorological conditions, which are favourable for fog formation. In contrast, the model shows a large error in near-surface relative humidity and temperature for false alarm cases compared to successful cases. The predicted near-surface wind direction is often in the southeast of the actual wind direction, which is prone to introduce cold bias and overprediction of relative humidity. False favourable temperature and humidity conditions lead to false sea fog alarms.