The　cables　of　a　cable-stayed　bridge　are　susceptible　to　structural　degradation　due　to　environmental　corrosion　and　fatigue,　which　directly　affects　the　safety　and　operational　performance　of　the　bridge.　As　the　process　of　the　degradation　in　practice　is　very　slow,　it　is　difficult　to　be　monitored　during　the　bridge　service　life.　Hence,　this　study　aims　to　develop　a　novel　semi-Markov　process　based　digital　twin　(DT)　framework　for　safety　evaluation　of　cable-　stayed　bridges　considering　cable　corrosion.　The　framework　encompasses　a　physical　twin　layer,　a　DT　layer　and　the　information　interaction　medium.　The　physical　twin　layer　mainly　comprises　the　bridge　physical　entity　and　its　associated　monitoring　system　that　provides　a　variety　of　perceptual　data　for　DT　modeling.　In　the　DT　layer,　the　DT　model　acts　as　a　virtual　counterpart　of　the　physical　bridge　for　mirroring　and　forecasting　the　bridge＇s　mechanical　behaviors.　The　information　interaction　medium　plays　a　crucial　role　in　the　bidirectional　information　communication　between　the　physical　and　digital　twin　layers.　Two　types　of　information　interaction　media　have　been　utilized　including　a　cable　force　influence　matrix　and　a　semi-Markov　process.　The　former　enables　updating　the　DT　model　to　precisely　match　the　data　measured　from　the　physical　bridge.　Meanwhile,　the　semi-Markov　process　depicts　the　probability　of　the　bridge＇s　condition　considering　the　cable　corrosion　during　the　different　service　periods.　The　proposed　procedure　can　predict　the　bridge　state　and　evaluate　the　safety　by　comparing　the　predicted　state　with　the　monitored　values.　The　proposed　framework　has　been　successfully　validated　on　a　real-world　cable-　stayed　bridge.　The　results　showed　the　proposed　DT　framework　was　reliable　and　effective　for　evaluating　the　bridge　condition.