The surface of saline-alkali soil is often accompanied by a complex network of shrinkage cracks. Investigating the characteristics of shrinkage cracks in saline-alkali soil and the distribution of soil salinity during the dynamic evolution process is of significant importance for scientifically formulating leaching regimes to mitigate soil salinity. Indoor soil grids were employed to investigate the dynamic evolution characteristics of shrinkage cracks in saline-alkali soil and conduct salt leaching experiments. Three initial soil salinity levels were set at 2g/kg (S1), 5g/kg (S2), and 8g/kg(S3). Digital image processing technology and morphological algorithms were employed to obtain geometric parameters and connectivity indices of the soil cracks. The evolution process of shrinkage cracks during the drying-wetting cycles in soils with different initial salinity levels was analyzed, and simultaneous investigations were conducted into the dynamic variations of soil salinity during crack evolution. The results indicated that during the process of soil shrinkage and cracking (soil dehumidification), an increase in initial soil salinity corresponded to increases in the crack area ratio, mean width, length density, and connectivity index. Moreover, within a single wet-dry cycle, the crack area ratio and mean width form an “∞” ring shape. Concurrently, soil salinity gradually migrated toward the vicinity of the cracks, ultimately leading to a non-uniform distribution pattern with higher salinity at the edges of the crack network and lower salinity within the grid. During soil shrinkage and cracking, the coefficient of variation of soil salinity content within treatments S1, S2, and S3 was increased as soil moisture was decreased, reaching 0.235, 0.247 and 0.251, respectively, after crack development stabilized (at soil water content of approximately 5%). In the process of soil salinity leaching (soil hygroscopic), the crack area ratio in treatment S3 was increased by 8.565 percentage points and 4.208 percentage points compared with that of treatments S2 and S1, respectively, with corresponding increase in soil desalination rates of 20.4% and 67.3%. Overall, higher initial soil salinity resulted in a greater soil leaching desalination rate. The final soil desalination rates for treatments S3, S2, and S1 were 54.2%, 45.0%, and 32.4%, respectively (P<0.05). Overall, the research result elucidated the dynamic evolution characteristics of shrinkage cracks in saline-alkali soil and unveiled the intricate relationship between crack evolution and soil salinity distribution. The findings can offer valuable insights into the formulation of effective soil improvement strategies to mitigate soil salinity issues.