In order to study the effect of the modifier (cement and curing agent) on the soil permeability and micro-pore distribution, we studied the permeability of the modified soil and the micro-pores using the permeability test and the mercury intrusion test, with the silty clay in plain reservoirs as the research object. The results showed that the curing agent reduced the pore volume and the permeability coefficient of the modified soil, but the decline was not linear. When the content was 2%, there was an obvious inhibitory effect between the cement and the curing agent. The fast hardening of the curing agent could significantly shorten the construction period. This points out a new direction for engineering repair. In addition, the cement had the greatest influence on the permeability of modified soil. With the increase of cement content, the large pores within the soil would transition to small pores. After 7 days, the soil permeability declined sharply, the amount of large and intermediate pores decreased, and the micro-pores and ultra-micro-pores increased. This study has established a functional relationship between the permeability coefficient and the porosity of large pores and medium-large pores, and can provide a theoretical basis for the stability analysis of the modified soil as impervious material.