Abstract: The study and evaluation of primary stress of tunnel surrrounding rocks is a necessary premise of conducting stability analysis of surrounding rocks and achieving and quick safe tunnel excavation.Two methods,including displacement back analysis and in-situ geological structure stress analysis,are taken to conduct grading cvaluation on primary stress condition in a railway tunnel.The study results show that the direction of paralleling axis of the tunnel on cross section is the direction of maximum main stress,and both the maximum main stress and the minimum main stress in surrounding rocks are larger than self-weight stress,and the ratio of stress to strength in surrounding rocks will be large.Therefore,the surrounding primary stress state in the tunnel is in high level earth stress.