Abstract: Active tectonic movement and hydrothermal activity have led to the development of abundant altered soft rocks within the Jinsha River suture zone. These altered soft rocks exhibit significantly pronounced undesirable engineering geological properties upon water exposure, posing severe potential hazards. This paper focuses on the altered soft rocks in the source area of the Baige landslide in Jiangda County as a representative case study. Using integrated techniques including field investigation, X-ray diffraction(XRD),scanning electron microscopy(SEM),immersion disintegration test, and triaxial compression experiments, we analyzed the material composition, microstructural characteristics, and hydro-physical properties of altered soft rocks. The degree of alteration is classified by combining macroscopic characterization and disintegration index, and the relationship between the shear strength characteristics and moisture content of different altered soft rocks is analyzed. The results show that in the source area of the Baige landslide, there are various types of altered rock masses such as talcum-altered, serpentine-altered, and clay-altered. Among them, clay-altered rocks have the highest degree of alteration, containing a large amount of clay minerals, accounting for as high as 50.84%,mainly composed of chlorite, illite and imon mixed layers. This kind of altered soft rock has highly developed internal pores, a loose overall structure and poor resistance to disintegration. With the increase of moisture content, due to the significant reduction of frictional resistance and cementation strength between clay particles, the cohesion and internal friction angle decrease by more than 50% and 20% respectively. However, for the altered rocks mainly characterized by talcum-altered and serpentine-altered, the content of clay minerals is only 7.62% and 15.95% respectively. As the moisture content gradually rises above the plastic limit, the cohesion of both types of specimens decreases significantly. And their internal friction angles exhibit complex variation trends, showing a gradual increase and an initial decrease followed by an increase, respectively. This change is closely related to the alterations in the structure and content of coarse particles in these altered rocks after they soften upon contact with water. The above research results have important reference value for deepening the understanding of the engineering geological characteristics of altered soft rocks in the Jinsha River suture zone.