Precipitation　calculation　is　one　of　the　fundamental　issues　to　resolve　in　Meteorological　Analysis　Processing　System.　At　present,　the　linear　interpolation　algorithm　is　widely　used　in　precipitation　calculation.　As　the　result　of　rough　results　that　the　linear　interpolation　got,　an　interpolation　method　of　combination　of　Shepard　Interpolation　Method　and　Sibson　Interpolation　Method,　which　is　used　in　precipitation　calculation　field,　has　been　proposed.　Based　on　the　decision　of　sparse　rainfall　areas　or　dense　ones,　this　method　uses　Shepard　method　to　deal　with　sparse　line　areas,　and　uses　Sibson　method　to　deal　with　dense　line　areas.　Finally,　the　experimental　results　show　that　the　method　has　obvious　advantages,　compared　with　linear　interpolation　algorithm.