SVPWM　algorithm　is　widely　used　in　the　field　of　power　electronic　frequency　conversion　power　supply,　motor　frequency　conversion　control,　power　quality　optimization　and　other　technical　fields.　In　this　paper,　the　principle　of　SVPWM　modulation　is　analyzed,　in　order　to　make　the　over-modulation　algorithm　more　simplistic,　the　adverse　effects　on　the　system　are　smaller,　and　a　phase　and　amplitude　are　used　to　change　the　modulation　method　to　optimize　the　algorithm　of　the　cross　modulation　II　zone[1,2].　And　using　Matlab　software　to　build　SVPWM　model　for　simulation　verification.　Explains　the　correctness　of　this　method.