Yangbajing Geothermal Field,located in the northern part of Yadong—Gulu Rift in Xizang（Tibet）is a famous high-temperature geothermal field in China.To better understand the development geothermal characteristics in the south Tibet,it is essential to study the temporal and spatial evolution of hydrothermal alteration. Based on the surface investigation,microscopic observations and X-ray diffraction analysis of the Yangbajing Geothermal Field and its hydrothermal altered rocks,the major alteration types and characteristics are summarized.The authors subdivided four different hydrothermal alteration zones: yellowish-brown center zone,grayish- white intensely altered zone,grayish-white medium altered zone and light-grayish weakly altered zone.There are three stages of alteration: the reddish-brown to yellowish-brown alteration stage,grayish-white alteration stage and light yellowish-gray alteration stage.The results show that the high-temperature geothermal activity center of Yangbajing Geothermal Field has always been in the sulfur valley of the north area, and its hydrothermal alteration activity is mainly controlled by the active fault in Yadong—Gulu rift,and is also synchronous with the fault activity.In the early stage,the geothermal water is directly discharged along the NE- trending faults,whereas in the late stage,it is discharged after runoff through the shallow Quaternary stratum,resulting in shifting from direct discharge to indirect discharge.The discharge area of medium—high temperature geothermal water migrated from the northern sulfur valley to the Zangbuqu area in the south. According to the results,we concluded that the intersection of NE-trending faults and NW-trending faults in the Liuhuanggou area can be regared as the main target for deep geothermal exploration in the north part of Yangbajing Geothermal Field.