Abstract: The differences of synoptic physical condition between the mesoscale convective complex (MCC) on June 22—23, 2002 and the meso-β-scale convective cloud clusters (MβCCC) on July 23—24, 2002 are analyzed by using NCEP/NCAR 1°×1° reanalysis data as well as GMS infrared body temperature (TBB) data. Results demonstrate that the MCC develops in a weak baroclinic environment, a 850 hPa horizontal wind shear line with a vortex dominated in the low levels and an anticyclone in upper levels, without baroclinic wave trough accompanying in midlevels. In contrast to MCC, the MβCCCs tend to develop in the right entrance region of a mean 200 hPa jet stream. Although the low level conditions are quite similar for both MCC and MβCCC, the evolution of the MβCCC is more related to a midlevel short-wave trough (main forcing) more than MCC, which is driven by a low-level θ_se gradients. Evidence also supports that the MCC needs abundant higher energy supply than the MβCCCs with larger and deeper θ_se tongue and a broader convective instability area.