Synthesized X-band dual-polarization Doppler radar data and the ambient temperature are used to explore the correlation between the microphysical properties and lightning activity of thunderclouds. After pre-processing of the radar data via the Z_H-K_DP correction, fuzzy logic-based classification of hydrometeors is conducted in a typical thunderstorm process in Sichuan basin, China. The results are combined with the cloud-to-ground (CG) lightning observation for a comprehensive analysis, which show significant correspondence between lightning flash and the solid microphysical particles. In low levels below the freezing level, the CG lightning activity corresponds with heavy rainfall, while it displays graupel or mixed ice-phase particles above the freezing level. The size of graupel echo coincides with the CG lightning activity largely. The CG lightning occurrence is strongly correlated with the convective intensity of thunderclouds, especially the ice-phase particles being dominated by graupel. The strong echo indicates the intensive CG lightning activity very well above the freezing level. Strong CG lightning activity often corresponds to a high cloud top and a large graupel area in the thunderclouds. Consequently, the region of mixed ice-phase particles, especially the region of mixed dry and wet graupel, can be regarded as an important spatio-temporal indicator of the CG lightning activity. Significant linkage between the microphysical properties and lightning activity is revealed above the freezing level in convective clouds in Sichuan basin, which provides a valuable indicator of lightning disasters for numerical weather prediction.