Based on analyses on mineral composition, mechanical property and hydrology property, three kind of samples are made in both drying state and saturated state respectively. Large-scale triaxial shear test, compression test and vibration test are applied on these samples. Through comparative analysis of test data, wet-chemical property of the samples is studied. Studies show that three samples have wet-chemical property in saturated state, which appears as decreasing of strengthen and increasing of deformation. Mechanism of wet-chemical property is also studied in two ways. On the one hand, filling particles is lubricated by water and re-construction of structure takes place between particles. On the other hand, soften and wet-chemical properties of mineral component are the internal factor causing the deformation. At last, some suggestions are given on construction of roadbed filled with this highly weathered rock.