Fracture　toughness　of　X80　pipeline　steel　in　a　simulated　petrochemical　environment　is　studied　in　this　paper.　Original　specimens　and　saturated　H2S　pre-corroded　specimens　were　tested　respectively　and　δ-Δa　resistance　curves　were　obtained,　while　the　influence　of　hydrogen　sulfide　corrosive　environment　on　the　resistance　curve,　fracture　toughness　and　plastic　work　of　X80　pipeline　steel　was　analyzed.　It　follows　that　the　lower　limit　of　KIC　of　the　pre-corroded　X80　steel　is　75.43　MPa·m½,　and　the　hydrogen　sulfide　corrosion　affect　significantly　on　the　fracture　toughness　of　X80　steel:　the　crack　growth　resistance　curve　obtained　from　original　specimens　is　much　higher　than　that　of　the　pre-corroded　specimens;　the　fracture　toughness　of　stable　crack　propagation　δ0.2BL　is　0.740　mm　and　0.365　mm　respectively,　and　the　former　is　2.02　times　of　the　latter.　In　case　for　a　given　amount　of　crack　propagation　Δa,　the　plastic　work　of　the　original　specimen　is　about　2.29　times　of　the　pre-corroded　specimen.　Hydrogen　sulfide　corrosion　reduced　the　fracture　toughness　of　the　X80　steel　remarkablely.　Thus,　in　the　course　of　natural　gas　pipeline,　hydrogen　sulfide　corrosive　environment　should　be　avoided　to　keep　the　steel　a　proper　high　toughness　to　prevent　damage.　©　All　right　reserved.