Based　on　abc　fundamental　reference　axis　system,　the　dynamic　process　of　a.c.　machine　with　PWM　control　is　discussed　in　detail.　The　induction　machine　is　a　non-linear　high-order　system.　And　this　system　become　more　complicated　when　non-sinusoidal　PWM　power　source　is　introduced　to　motor.　Therefore,　the　machine　behave　in　continuous　periodic　transient　process.　States　according　to　switch　pattern　for　the　machine　performance　supplied　by　PWM　including　dead-band　interval　preventing　shoot-through　fault　are　studied　in　detail,,　mathematical　model　is　established.　The　performance　of　machine　powered　by　PWM　is　explored　based　on　abc　frame.　The　simulation　result　using　MATLAB　is　also　presented.