Abstract: Based on the field survey for hydrogeology and engineering geology along the Qinghai-Tibet Railway made in 1975~1977,consulting the results obtained recently by the other people,the active tectonics,geological hazards and the engineering assessment on the Qinghai-Tibet Railway are expounded in the paper.The relationship between active tectonics and modern and fossil earthquakes,the relationship between active structural belt and earthquakes structural belt,dating of active faults and their active rate,the relationship between active fault and earthquake surface rupture,the earthquake period in the main earthquake structural belts are placed emphasis on. According to above mentioned active faults and earthquakes,in consideration of the geological hazards,the 4 types of section of engineering geology of the Xidatan-Lahsa Section along Qinghai-Tibet Railway are given in the paper.They are ①good;②general;③bad;④extremely bad.