Shallow　buried　tunnels　are　commonly　seen　in　engineering　practice.　To　understand　the　failure　mechanism　of　a　shallow　buried　tunnel　is　of　significance　in　engineering　practice.　There　is　a　reasonable　judging　index　lacking　in　tunnel　stability.　The　strength　reduction　method　(SRM)　gained　limited　status　of　geotechnical　materials　by　reducing　the　computation　parameters.　Then,　the　failure　zone　can　be　obtained　and　shown.　Finally,　a　safety　factor　can　be　obtained　by　this　progress.　This　method　has　been　used　in　slope　stability　analysis.　The　usage　of　this　method　is　a　new　field.　Based　on　shallow　tunnel　computation　model　under　different　cover　depth,　the　SRM　method　is　adopted　in　finding　the　safety　factor　of　shallow　buried　tunnels.　The　displacement　curve,　changing　with　the　strength　reduction　factor,　is　drawn　and　the　catastrophe　point　is　found　as　the　safety　factor.　Further,　in　comparison　with　the　failure　criteria　of　plastic　zone　connection　and　non-convergence,　and　also　compared　with　model　tests,　failure　mechanism　of　shallow　buried　tunnels　is　analyzed.　Specialty　of　these　safety　factors　is　discussed　and　it　is　proved　that　they　maintain　accordance.　This　research　is　significant　for　a　tunnel　safety　factors　study.　©　2014　American　Society　of　Civil　Engineers.