The　migration　and　leakage　of　formation　fluid　along　the　cement　plug/formation　interface　negatively　affects　the　integrity　of　open-hole　temporary　abandoned　wells.　A　3-D　numerical　model　is　developed　based　on　the　cohesive　zone　method　for　analyzing　the　initiation　and　propagation　of　fractures　along　the　cement　plug/formation　interface.　The　model　is　validated　by　comparison　with　an　existing　microannulus　model　to　demonstrate　its　reliability.　The　relationship　between　fracture　development,　propagation　pressure,　and　fluid　migration　time　in　the　damage　evolution　of　the　interface　is　quantitatively　analyzed,　and　the　influences　of　different　mechanical　parameters　on　fracture　propagation　pressure　and　debonding　height　are　studied,　including　cement　plug　mechanical　parameters,　formation　mechanical　parameters,　horizontal　in-situ　stress,　and　interface　cementation　strength.　The　simulation　results　indicate　that　(1)　high　interface　cementation　strength,　cement　plug　elastic　modulus,　and　formation　elastic　modulus　tend　to　increase　fracture　propagation　pressure　and　decrease　fracture　debonding　height,　which　helps　to　mitigate　debonding　failure　of　the　cement　plug/formation　interface.　(2)　Large　horizontal　in-situ　stress　can　constrain　fracture　propagation　when　the　stress　is　uniform.　For　a　non-uniform　horizontal　stress,　a　large　in-situ　stress　difference　is　more　likely　to　cause　fracture　extension.　(3)　The　fracture　propagation　pressure　and　fracture　debonding　height　of　the　cement　plug/formation　interface　are　less　affected　by　the　Poisson＇s　ratio　than　the　elastic　modulus　of　the　formation　and　the　cement　plug.　The　numerical　model　established　in　this　study　provides　an　effective　method　to　evaluate　the　well　integrity　failure　of　open-hole　temporary　abandoned　wells　due　to　debonding　failure　of　the　cement　plug/formation　interface.