Abstract: The Jiali fault is one of the major active faults in southeast Tibet Plateau. In recent years,many major engineering projects,such as railways,highways,and hydropower plants,have been or are being constructed in southeast Tibet. Engineering geological disasters associated with Jiali fault have brought great challenges to the construction,operation,and maintenance of those major projects. Previous studies on Jiali fault have mainly focused on its activities in Holocene. Its engineering geomechanical characteristics have not been well addressed. Major engineering projects are densely distributed in the middle segment of Jiali fault. This study,based on plenty of materials data obtained from a throughout field survey,presents an engineering geomechanical analysis on middle Jiali fault. The results show that,in middle Jiali fault,engineering geomechanical factors(include geomorphology,rock combination,rock mass structure,in-situ stress,shear zone characteristics,and Quaternary activity. They have typical sectional distribution characteristics. The engineering geomechanical model within middle Jiali fault can be categorized into two types: (1)a "ductile" engineering geomechanical model in the section near the East Himalaya Syntaxis(EHS); (2)a "brittle" engineering geomechanical model in sections far away from the EHS. The formation of the two different models is mainly affected by the strong metamorphic belt with high temperature and pressure,which is generated by the hot mantle flow under the EHS. Based on the subsection characteristics of the engineering geomechanical model,this paper further discusses some important engineering geological problems and relevant disaster characteristics in different sections of middle Jiali fault. This study is expected to provide a theoretical reference for constructions of major projects and mitigations of geological hazards in the southeast Tibet.