As　the　power　output　of　wind　farm　has　strong　randomicity,　the　reactive　power　optimization　and　system　stability　of　grid-connected　wind　farm　are　researched.　A　particle　swarm　optimization　algorithm　based　on　stochastic　simulation　technology　and　Beta　distribution　function　is　proposed　with　the　reactive　power　compensation　model　based　on　constrained　programming.　The　implementation　techniques　of　the　algorithm　based　on　Beta　distribution　are　discussed,　i.e.　Beta　distribution　function,　the　tactics　of　initial　possibility　solution　and　the　tactics　of　particle　swarm　renewing,　as　well　as　the　detailed　optimization　calculation　process.　Examples　of　the　optimization　of　reactive　power　compensation　and　the　checkout　of　system　stability　for　grid-connected　wind　farm　verify　that　the　proposed　model　can　meet　the　need　of　compensation　capacity　calculation　under　reliable　and　economic　conditions　with　good　effect.