Abstract : Research purposes : Jinshajiang combination zone is a lithosphere fracture belt that Sichuan - Tibet railway cannot avoid. The activity and stress - strain of crustal rock in fault zone have constrained the railway engineering seriously. Based on field investigation on geology - tectonic features and earthquake，combining regional geophysical and deep tectonic information，a geotechnics conceptual model of crustal structure of Jinshajiang combination zone was established. The stress，strain and deformation characteristics were analyzed by using ANSYS finite element numerical simulation method. Research conclusions: ( 1 ) Jinshajiang combination zone is a reverse fault with strong compressive property. (2) Two high - conductivity weak layers in the crust flow to NE driving upper rock， forming a dynamic model like 11 conveyor belt". (3 ) The migmatite on the west of Jinshajiang combination zone breaks the crustal horizontal continuity， plays a shielding role in the stress and movement of crust. (4) The effects of combination zone on railway engineering were compressive deformation along NE，high ground stress of tunnel in the magmatite region，and large deformation of soft rock on the east of combination zone. (5)The research results can be applied to planning and design of Sichuan - Tibet railway and otlier similar railways.