A　novel　method　of　pipeline　pigging　is　that　Coiled　Tubing　(CT)　connected　with　a　pig,　and　then　CT　is　injected　into　the　SCR　to　clean　up　pipelines.　The　CT　needs　enough　axial　force　so　that　it　would　not　be　stuck　in　the　SCR　during　the　pipeline　pigging　operation.　To　analyze　the　axial　load　transfer　characteristic,　paper　built　the　force　analysis　of　the　micro　element　on　the　straight　and　curved　section,　amended　effective　axial　force　and　the　friction　between　the　CT　and　SCR,　and　built　the　mathematical　model　of　SCR　pipe-in-pipe　system　considering　impacts　of　the　coiled　tubing＇s　budding.　The　axial　force　of　the　random　micro　section　can　be　calculated　through　iterative　method.　In　order　to　verify　the　correctness　of　the　theory,　the　SCR　pipe-in-pipe　system＇s　indoor　platform　was　built.　The　experimental　platform　can　study　different　effects　which　affect　the　CT＇s　load　transfer　behavior　within　the　unfixed　SCR.　The　experimental　results　of　two　different　phases　which　inclined　angles　were　2.0　degrees　and　30.0　degrees　show　that　CT＇s　transfer　efficiency　of　axial　load　is　less　than　85.0%　in　SCR　pipe-in-pipe　system,　and　it　will　increase　with　the　inclined　angle　increasing.　Through　comparing　experimental　and　theoretical　calculation　results,　the　mathematical　model　of　SCR　pipe-in-pipe　system　is　validated.　Paper　calculated　the　axial　force　results　on　the　inclined　angle　2.0　degrees,　10.0　degrees,　18.0　degrees,　26.0　degrees　and　30.0　degrees　by　the　theoretical　mechanical　model.　The　theoretical　calculation　results　show　that　the　transfer　efficiency　would　increase　with　the　increasing　of　the　inclined　angles.　To　ensure　more　axial　force　to　be　transferred　to　the　CT＇s　bottom-end,　the　inclined　angle　should　be　as　big　as　possible.　The　above　research　can　provide　theoretical　support　to　the　SCR＇s　pigging　operation.