A　PEO/CrAlSi　composite　coating　of　similar　to　10　mu　m　thick　on　Zr-2　alloy　was　prepared　by　duplex　plasma　electrolytic　oxidation　(PEO)　and　filtered　cathode　vacuum　arc　deposition　(FCVAD)　techniques.　The　high　temperature　steam　oxidation　behavior　of　bare　and　PEO/CrAlSi-coated　Zr　alloys　was　performed　in　1000-1200　degrees　C.　Their　morphologies,　microstructures,　compositions　and　phase　components　were　analyzed　by　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),　X-ray　diffraction　(XRD)　and　glow　discharge　optical　emission　spectrometer　(GDOES).　The　effects　of　Al　and　Si　elements　on　multilayers　microstructure　evolution　of　coated　Zr-2　alloy　at　steam　atmosphere　were　discussed.　It　was　found　that　the　composite　coating　significantly　improved　the　high-temperature　steam　oxidation　resistance　of　Zr-2　alloy.　The　mass　gains　of　the　PEO/CrAlSi-coated　Zr-2　alloy　after　3600　s　exposure　in　1000　degree　celsius,　1100　degrees　C　and　1200　degrees　C　steam　were　28　%,　29　%　and　44　%　of　the　bare　alloy.　Through　the　oxidations,　Al　diffused　both　inward　and　outward　to　the　substrate　and　the　surface　regions,　respectively.　Formation　of　a　top　oxide　layer　(Al2O3,　Cr2O3)　greatly　suppressed　the　inward　oxygen　diffusion.　The　Si　enrichment　in　the　PEO　interlayer　formed　a　Zr2Si　layer,　which　inhibited　the　Cr-Zr　interdiffusion　at　1000　degree　celsius　and　1100　degree　celsius.　At　1200　degree　celsius,　the　Zr2Si　layer　was　oxidized　and　the　CrZr2　phase　was　formed　in　the　Zr　alloy　substrate　especially　at　the　beta-Zr/alpha-Zr(O)　interface.