The　thermophysical　properties　of　arc　plasma　provide　reliable　micro-theoretical　foundations　and　parameter　inputs　for　the　numerical　simulation　of　the　air　arc　discharge　process.　Based　on　the　assumption　of　the　local　thermodynamic　equilibrium,　the　computation　of　transport　properties　including　electron　diffusion　coefficient,　viscosity,　thermal　conductivity　and　electrical　conductivity　is　performed　by　using　the　Chapman-Enskog　method　and　expanding　the　sonine　polynomial　up　to　the　third-order　approximation　(second-order　for　viscosity)　in　a　pressure　(0.1-20　atm)　and　temperature　range　(300-40000　K)　conditions　which　satisfy　most　thermal　plasma　modelling　requirements.　The　most　recent　data　on　potential　interactions　and　elastic　differential　cross　sections　for　interacting　particles　are　utilized　to　determine　the　collision　integrals,　resulting　in　more　accurate　and　reliable　values　of　transport　properties　than　those　given　in　the　previous　literature.