With hourly intensive surface observations, satellite remote sensed temperature of black body (TBB) and 3 hourly radio soundings, an analysis is carried out to investigate the diurnal changes of convective rainfall and atmospheric physical variables along the middle valleys of Yangtze River. The results are as follows： the convective rainfall is of obvious diurnal changes, with a rainfall maximum (minimum) at 1500 BT (0100 BT). The surface and sounding physical variables are also of clear diurnal changes. The diurnal variation of surface temperature is the most obvious, with a mean diurnal range of 9℃, while the diurnal range of dew point temperature is only about 1℃. The diurnal change of relative humidity is mainly caused by the temperature diurnal variation. The spatial distribution of surface temperature diurnal changes is influenced by the topography. The temperature rising (dropping) in the mountainous areas is larger than in the plain areas in the daytime (nighttime). The diurnal change of temperature gradient due to the topographic difference can drive topographically near surface thermal flow. The convergence (divergence) flows occur in the mountainous areas (plain areas) in the daytime, vice versa in the nighttime. The stability decrease in the lower atmosphere and the CAPE increase are beneficial to the afternoon thermal convection initiation in the daytime. The lowering of lifting condensation level (LCL), the increase of relative humidity and the increase of air column precipitable water vapor (PW) are favorable for the development of long life early morning convective systems in the nighttime.