In　order　to　compensate　for　the　effects　of　supply　voltage,　process　and　temperature　on　the　oscillator　frequency,　we　design　a　ring　oscillator　with　digital　calibration.　By　comparing　the　frequency　deviation　between　the　ring　oscillator　and　the　external　reference　clock　source,　adjusting　the　state　of　the　control　word,　and　then　changing　the　number　of　resistors　in　the　analog　circuit　to　adjust　the　output　frequency　of　the　ring　oscillator,　so　as　to　compensate　the　output　frequency　deviation.　Firstly,　we　analyze　the　analog　circuit　and　digital　circuit,　and　then　get　the　result　of　simulation,　finally　carry　out　the　layout　design.　Simulation　results　show　that　by　digital　calibration,　the　output　frequency　can　be　adjusted　up　or　down　by　30%,　so　that　the　deviation　can　be　compensated　to　a　great　extent.