The parameters of substrate related to clogging, such as the grain size, the filtration rate and organic substance in the substrate, were investigated in the integrated vertical-flow constructed wetland (IVCW). The substrate of IVCW was collected by a specific sampling tube in situ and the infiltration experiment showed that the filtration rate of substrate increased with the depth of substrate and the minimum filtration rate existed 15-30 cm below the surface of substrate. The amount of organic substances in upper 15 cm layer of the substrate was limited and even less in deeper layer after fifty two-month running, and this revealed that IVCW was operating steadily and no clogging was observed. Considering the factors related to clogging, the strategy to prevent and recover the clogging phenomenon was put forward.