The　plasma　sprayed　ZrO2-7　wt%Y2O3　(7YSZ)　coating　has　been　widely　applied　in　aircraft　engine　as　a　thermal　barrier　coating.　In　this　study,　the　duplex　TBC　system　(MCrAlY　+　7YSZ)　were　deposited　onto　304　stainless　steel　substrate　by　APS.　Four　principal　spraying　parameters　during　the　deposition　of　7YSZ　coating　were　optimized　by　using　orthogonal　experimental　design,　including　the　stand-off　distance,　plasma　power,　preheating　temperature　and　powder　feeding　rate.　Their　influences　on　the　coating＇s　microstructure,　adhesion　and　its　mechanical　properties　were　studied　and　the　optimized　parameters　were　finally　obtained.　The　results　showed　that　the　dependence　of　the　spraying　parameters　on　the　properties　of　7YSZ　coating　is　highly　correlated　to　the　melting　condition　of　the　in-flight　particles.