Abstract: Through direct shear test and microscopic scanning electron microscope test, the variation of unsaturated coal soil macroscopic parameters with moisture content and the number of dry-wet circulation under the dry-wet circulation was studied. The microstructure parameters which significantly affect the strength parameters were obtained by grey correlation analysis. The results show that the shear strength and total cohesion of coal measure soil samples decrease gradually with the increase of moisture content, and the deterioration occurred with increasing number of dry-wet circulation. The degree of deterioration is higher after one dry-wet circulation, and tends toward stability after three cycles. The moisture content and the number of dry-wet circulation have little effect on the total internal friction angle. However, with the increase of water content and the number of dry-wet circulation, the average diameter and number of large particles of coal-bearing soil decreased, the average diameter and number of large pores increased, the shape of particles tended to be simple, the shape of pores tended to be round, and the arrangement of particles became more orderly. In the dry-wet circulation process, the macroscopic total cohesion was closely related to the microstructural parameters such as porosity, particle fractal dimension, particle orientation probability entropy and particle average diameter. In conclusion, the disintegration, fragmentation and cementation of coal-bearing soil particles caused by dry-wet circulation were the main reasons for the deterioration of shear strength of coal-bearing soil.