Supercritical　CO2　pipelines　usually　are　used　to　link　the　CO2　capture　system　to　the　geological　storage.　There　are　severe　hazards　once　the　asphyxiating　gas　leaks　from　the　long-distance　pipeline.　The　uncertainty　of　near-field　jet　characteristics　results　in　imprecise　consequences　assessment　of　accidental　release　of　supercritical　CO2.　To　improve　the　prediction　of　consequences　of　accidental　release　accuracy,　the　near-field　mechanisms　of　flashing-spray　jet　was　investigated.　In　this　work,　an　experimental　setup　with　multiple　measurement　instruments　was　developed　to　impose　controllable　CO2　release　from　a　high-pressure　vessel.　The　flashing-spray　jet　structures　of　supercritical　CO2　from　circular　and　rectangular　orifices　were　recorded　by　a　high-speed　camera.　Results　indicate　that　the　near-field　structures　of　supercritical　CO2　jet　from　circular　and　rectangular　orifices　are　totally　different,　which　causes　the　different　dispersion　consequences.　The　jet　angle　and　shock　waves　were　analyzed　quantitatively.　Lastly,　the　models　of　flashing-spray　based　on　the　two　different　phenomena　from　rectangular　and　circular　orifices　were　discussed.　The　combination　of　macroscopic　and　microscopic　data　in　the　jet　can　help　to　understand　the　complex　physics　and　improve　discharge　and　dispersion　model.　This　work　provides　a　fundamental　data　to　consequences　assessment　of　accidental　release　of　supercritical　CO2.　©　Copyright　©　2021　Teng,　Bai,　Li　and　Wang.