Research conclusions: The alignment o f ra ilway w as lim ited because o f the un favorable geo log ical cond it ions in the crossing- mountain area. Based on the research, itw as decided the a lignmen t o f the railw ay w ou ld be straight and pass by the area w ith the unfavorable geolog ical cond it ions as much as possib le. When the alignment of the ra ilw ay had to pass through the area w ith unfavorable geo log ica l cond itions, the nature, scale and harm ful degree o f the unfavo rable geo log ical cond itions would be detected clearly at first and then the opt iona l alignment schemes w ou ld be compared in techno logy and economy. Through the research, the alignment avo ided severa l goa fs andmost of the dangerous rocks to much improve the eng ineering geo log ica l cond it ions and techn ica l conditions and ensure the construction safety and the safety of railw ay serv ice. In addition, the ra ilw ay leng th w as shortened by 67 212m, w ith sav ing the construction cost o f 8 758. 8m illion Yuan ( RMB ) and achiev ing good social and econom ic bene fits.