The porosity of solid skeleton is changed under muddy water infiltration, and thus the permeability is also changed. A concentration of 30% muddy water compared with clear water, is experimented to simulate the movement of small particles. The relationship between solid skeleton permeability, porosity and time is obtained from experiments. The relationships among fraction void and permeability coefficient in such cases are presented. The relationship expressions are studied. Some novel laws are obtained as follows: because of the hindrance effect by the small particles, permeability coefficient decreases gradually over time, but clear water has no influence on the permeability coefficient; at the beginning, the porosity of solid skeleton decrease rapidly over time. Then it is stabilized latterly, they two are in monotone decreasing parabolic curve relationship; The relationship curve of cumulative infiltration capacity and time is a monotonically increasing curve which slope becomes smaller; the infiltration concentration fall first and rises later. The results provide a theoretical basis for muddy water infiltration.