Desiccation cracking has a significant influence on the hydro-mechanical behaviour of soils. Most previous studies focus on the desiccation cracking of slurry soil samples, whereas little attention has been paid to compacted soils. This study aims to investigate the effects of microstructure on the desiccation cracking of a compacted lean clay. Five soil samples are mixed with different water contents including 12.5%, 14.5%, 16.5% (optimum water content), 18.5%, and 20.5%, compacted to generate different initial soil microstructures. After compaction, the soil samples are subjected to saturation and then the same drying process. The pore size distribution of each soil sample is characterized by performing mercury intrusion porosimetry (MIP) test. The change in water content and the evolution of surface crack pattern during the drying process are continuously monitored.