Abstract: Located in Erlang village, Gao Chuan township, Mianyang city, Sichuan province, the 1# inclined shaft of Yuelongmen tunnel of CLZQ-5 contract of Chengdu-Lanzhou railway, which is a newly-built railway, passes through Longmenshan fault zone with extremely complex geological conditions. The geological conditions in this area are extremely complex, showing typical characteristics of "four poles and three highs", namely, the terrain cutting is extremely strong, the structural conditions are extremely complex and active, the lithologic conditions are extremely weak and broken, and the Wenchuan earthquake effect is extremely significant. It is a dangerous mountainous area with complicated geological conditions. The tunnel portal construction of No.1 inclined shaft of Yuelongmen tunnel overcomes various unfavorable conditions and provides valuable experience for tunnel portal construction of railway engineering units under severe geological conditions.