This　paper　proposes　an　improved　alternating　current　(AC)　arc　model　based　on　the　Cassie-Mayr　hybrid　model　and　magnetohydrodynamics　(MHD)　theory.　The　undetermined　parameters　of　the　traditional　Cassie-Mayr　arc　model　are　mainly　obtained　by　subjective　methods　such　as　empirical　value,　approximate　expression,　and　indirect　estimation　which　are　complex,　inaccurate,　and　dependent　on　experimental　data.　To　overcome　these　disadvantages,　an　axisymmetric　two-dimensional　arc　model　is　established　based　on　the　MHD　theory,　and　the　undetermined　parameter　values　of　the　Cassie-Mayr　hybrid　arc　model　are　obtained　based　on　the　results　of　MHD　numerical　simulation.　The　accuracy　of　the　proposed　modified　Cassie-Mayr　model　is　verified　by　comparing　with　experimental　data,　and　the　results　of　the　modified　Cassie-Mayr　model,　traditional　Mayr　model,　and　Cassie　model　are　discussed.　The　arc　characteristics　of　serval　loads　are　studied　and　analyzed　based　on　the　modified　model.