Abstract：To study the weathering characteristics of tertiary pelitic siltstone, each silty mudstone with different weathering degrees is analyzed in many different experimentations. The researching fields involve its engineering characteristics, weathering durability and weathering speed. The engineering characteristics were revealed by testing mineral composition, chemical composition and mechanical properties of rock mass with different weathering degrees. The weathering durability was shown by testing compressive strength and slake durability of different rock samples. The weathering speed was determined in four different experimental conditions for the weathering rock. The test results show that with the growth of weathering degree of the rock mass, the content of clay minerals in the rock mass increases, the chemical composition with high activity in the rock mass decreases relatively, the dry density of the silty mudstone decreases, the total porosity and the water absorption rate of the silty mudstone increases, the mechanical properties are weakened, and the rock mass becomes easy to soften and collapse. At the same time, the weathering speed of the rock mass is related to the weathering degree and the exposed area of the rock mass. The research findings provide some theoretical basis for understanding the Tertiary Pelitic Siltstone and solving related problems in practical engineering.