On　the　key　problem　of　ineffective　representation　of　uncertain　variables　in　complex　system　simulation,　the　semi-quantitative　method　of　uncertain　variable　based　on　group　decision　and　cloud　model　is　proposed　to　process　the　uncertain　data.　Then　the　uncertain　knowledge　induction　based　on　cloud　model　is　proposed.　The　induction　process　and　method　is　given　in　the　paper.　This　method　is　combined　with　the　merit　of　conversion　and　fusion　quantitative　and　qualitative　of　cloud　model　in　induction.　Lastly　the　summary　and　future　research　is　given　at　the　end　of　study.