［Objective］ To mitigate the durability deterioration of slope engineering structuresinduced by prolonged groundwater seepage and corrosive medium corrosion，a modified mica/epoxycomposite coating with enhanced impermeability and corrosion resistance was developed to overcome the defect of insufficient protective performance of traditional epoxy coatings.［Methods］Mica powderwas surface-modified using the silane coupling agent KH-550 and subsequently incorporated into anepoxy resin matrix to fabricate the modified mica composite coating. The impermeability of coating wascharacterized via water absorption and water vapor barrier performance tests. The corrosion resistancewas evaluated through electrochemical measurements. Furthermore， the influence of KH-550 modification on the overall performance of coating was investigated by combining adhesion strengthtests with water contact angle measurements.［Results］KH-550 effectively improved the dispersion ofmica powder within epoxy resin. Compared with the unmodified system，the modified mica coatingsignificantly improved the interfacial bonding strength and surface hydrophobicity. The adhesion increased from 7. 38 MPa to 8. 01 MPa，and the water contact angle increased from 98. 27° to 111. 09°.Both the anti-seepage and anti-corrosion performance have been significantly enhanced. The watervapor transmission rate decreased from 175. 11 g/（m²·d） to 33.04g/（m²·d）， and the water vapor permeability coefficient decreased from 6. 47×10^-12 g·cm/（cm²·s·Pa） to 1. 36×10^-12 g·cm/（cm²·s· Pa）. After being immersed in a 3. 5% NaCl solution for 600 hours，the low-frequency impedance modulus of coating remained at 1. 04×10¹¹ Ω ·cm²，and the phase angle was 68°，demonstrating excellent shielding and protective performance.［Conclusion］ The KH-550 modification effectivelypromotes the uniform dispersion and interfacial bonding of mica powder within the epoxy coating. Theresulting modified mica coating not only significantly enhances the physical barrier performance butalso improves the adhesion to the metallic substrate，thereby providing a valuable technical referencefor the selection of anti-seepage and anti-corrosion materials in harsh environments such as slopeengineering.