A　method　of　precaution　control　based　on　optimal　dispatch　of　generation　is　proposed.　Firstly,　all　potential　faults　of　the　net　are　scanned　and　then　the　no-harmful　faults　are　excluded.　Ranked　by　the　product　of　EEAC　stability　margin　and　fault　probability,　the　critical　cluster　group　of　potentially　harmful　fault　can　be　identified.　Secondly,　the　limit　of　power　adjustment,　Δpmin　and　Δpmax,　can　be　determined　with　EEAC　sensitivity　analysis　method.　Thirdly,　the　ratios　of　active　power　adjustment　of　the　generators　are　determined　according　to　the　number　of　critical　generators　and　the　sensitivity　of　the　stability　margin　to　generator　output.　Finally,　the　optimization　of　precaution　control　can　be　transformed　into　the　optimal　output　dispatch　of　generators　which　are　chosen　in　last　step.　Simulation　results　in　New　England　10-generator　39-bus　system　show　the　feasibility　and　correctness　of　this　method.