In　this　work,　we　proposed　a　black　phosphorus　(BP)　achiral　metasurface　and　theoretically　study　the　chiroptical　response　arising　from　extrinsic　2D-chirality　in　the　mid-infrared　regime.　The　achiral　metasurface　is　composed　of　a　monolayer　BP　sheet　sandwiched　by　a　silver　ring　array　and　dielectric　spacer　stacking　on　a　silver　substrate.　The　giant　circular　conversion　dichroism　(CCD)　of　the　achiral　metasurface　is　allowed　at　oblique　incidence　for　the　cooperative　interaction　of　BP　anisotropic　surface　plasmon　modes　and　localized　surface　plasmons　in　metal　rings,　and　the　integrated　BP　can　dynamically　modulate　the　chiroptical　response　by　controlling　the　doping　concentration　of　BP.　Furthermore,　we　found　that　a　multiband　phenomenon　for　CCD　response　occurs　when　tuning　the　thickness　of　the　spacer.　The　proposed　hybrid　achiral　metasurface　provides　more　flexible　opportunities　to　realize　active　polarization　modulator,　biosensor　and　chiral　detection.　(C)　2022　Optica　Publishing　Group　under　the　terms　of　the　Optica　Open　Access　Publishing　Agreement