For　controlling　the　engine　exhaust　noise　at　real　time　on　line,　the　source,　transmit　mechanism　and　the　spectrum　character　of　the　diesel　exhaust　noise　were　analysed.　By　using　adaptive　control　technique　of　active　noise,　some　experiments　are　designed　to　control　exhaust　noise　of　diesel.　Experiment　results　show　that　exhaust　noise　of　a　diesel　could　be　attenuated　and　our　adaptive　control　technology　of　active　noise　could　control　diesel　exhaust　noise　at　real　time　on　line.