The　anticorrosion　mechanism　of　Al-Ti-Si-RE　coating　in　the　environment　of　simulated　deep　sea　was　investigated　using　electrochemical　measurement　and　micro-analysis.　The　result　shows　that　Al-Ti-Si-RE　coating　possesses　better　corrosion　resistance　at　hydrostatic　pressure　than　at　atmospheric　pressure.　After　480　h　immersion　at　3　MPa,　a　platform　similar　to　a　passivation　region　occurs　in　the　anode　of　the　potentiodynamic　polarization　curve　because　corrosion　products　block　the　corrosion　channels.　At　the　same　time,　at　hydrostatic　pressure,　electrochemical　impedance　spectroscopy　(EIS)　indicates　that　Al　passive　film　dissolves　within　6　h　of　immersion,　then　tends　to　be　stable　after　12　h,　and　hardly　changes　between　300　and　480　h.　To　further　analyze　the　original　corrosion　process,　electrochemical　noise　(EN)　of　0　similar　to　64　ks　at　0.1　and　3　MPa　was　measured,　which　quantificationally　described　the　corrosion　process　from　passive　film　dissolving　to　corrosion　product　fast-forming　to　stabilization.　From　morphology　observation　and　X-ray　diffraction　(XRD)　analysis,　the　rich　Ti　phase　(Ti-Al　intermetallics,　etc)　of　the　coating　is　cellular　and　has　good　corrosion　resistance,　whose　construction　could　fix　the　Al　oxide　inside　the　coating,　and　thicken　the　coating　to　inhibit　the　corrosion.