In　this　paper,　taken　a　steel　box　arch　bridge　as　background,　a　FEA　model　is　built　and　the　stability　is　analyzed,　including　buckle　stability　and　extreme　stability.　The　results　show　that　there　are　significant　differences　between　buckle　stability　factor　and　extreme　stability　factor.　It　is　a　must　to　pay　more　attention　to　arch　bridge　stability.