Based　on　the　finite　element　analysis　considering　dual-nonlinearity,　the　investigation　of　simple　method-　equivalent　column　method　to　calculate　the　critical　loads　of　concrete-filled　steel　tubular　arch　under　pure　compression　is　carried　out.　The　stability　factor　K1　considering　influence　of　rise-to-span　factor　and　the　discount　factor　K2　considering　effect　of　initial　crookedness　are　presented　for　equivalent　column　method.　Practical　formula　are　given　out　by　using　critical　load　of　short　column　in　different　CFST　structure　design　codes.　By　comparison　with　the　finite　element　results,　the　presented　method　can　estimate　nonlinear　critical　load　of　CFST　arch　under　pure　compression　accurately,　and　the　change　of　steel　ratio　and　steel　type　has　little　effect　to　its　precision.