Abstract: Using hourly ground observation, wind profile observation and weather radar observation, the diurnal variation characteristics of the reanalysis products of the Local Analysis and Forecasting System (LAPS_LIVE) and the fifth-generation reanalysis product of the European Centre for Medium-Range Weather Forecasts (ERA5) during the Meiyu period in 2020 were validated and analyzed. The results show that the correlation between the diurnal variations of surface fields in LAPS_LIVE and ground truth is higher than that in ERA5 overall. Specifically, LAPS_LIVE is not as good as ERA5 in terms of the diurnal variations of surface temperature and humidity in southwest mountainous area. LAPS_LIVE is obviously better than ERA5 in terms of the diurnal variations of sea level pressure and surface temperature and humidity in the Dabie Mountains area. The diurnal variations of sea level pressure and surface temperature and humidity in the Jianghan Plain have small biases for both reanalysis datasets. The bias of mean surface wind field in LAPS_LIVE is smaller than that in ERA5, but the diurnal variation in LAPS_LIVE is weaker and the wind speed is also lower. The diurnal amplitude and mean speed of surface wind in ERA5 are significantly stronger than the observations. The inertial oscillation characteristics of low-level wind profile in LAPS_LIVE are consistent with the observations. The time evolution and vertical shear of low-level wind field in the morning in LAPS_LIVE is better than that in ERA5, but the low-level jet at night in LAPS_LIVE is worse. ERA5 overestimates the low-level northerly winds and the southwest jet in the morning, but its average low-level wind field is closer to the observations than LAPS_LIVE.