Objective:　This　paper　introduces　a　comparable　optimized　PWM　ML4428　control　chip,　which　provides　all　the　functions　necessary　for　controlling　a　Blood　Pump.　The　Blood　Pump　is　based　on　an　Active　magnetic　Bearing　(AMB)　system.　Methodology:　Directing　to　the　dual-loop　speed　control　system　in　the　chip,　which　has　a　confined　range　of　speed-modulate　voltage,　A　speed-modulate　design　is　introduced　for　the　purpose　of　allowing　off-range　modulate　voltages　to　work.　This　module　serves　a　function　that　can　transform　the　off-range　modulate　voltage　into　within-range　modulate　voltage　through　a　digital　electrical　network　as　an　AD　converter　to　implement　PWM.　Conclusion:　and　Discussion　Based　on　this　module,　we　made　experiments　to　test　rev　of　the　Blood　Pump　under　the　condition　of　invariable　control　voltage　and　invariable　inlet　pressure　respectively.　The　result　shows,　with　inlet　pressure　of　22mmHg　and　control　voltage　of　22V,　the　rev　of　pump　can　be　up　to　8000rpm,　outlet　pressure　with　100mmHg,　and　flux　with　5L/min.　The　result　meets　our　initial　expectation.