After　collecting　the　general　characters　of　designing　ellipse　species　gears,　by　applying　high-order　deformed　ellipse　as　the　basic　mathematic　model,　whose　properties　are　common　to　ellipses,　the　CAD　system　was　built　with　VB　6.0　which　is　a　visual　and　object-oriented　program　language.　The　function　of　main　modules　and　the　realization　of　the　system　are　introduced.　Two　main　functions,　to　design　new　gears　and　check　the　test　data　of　a　real　gear,　are　achieved　in　the　CAD　system　by　fully　considering　the　individual　application　and　the　idea　of　designers.　This　provides　a　convenient　and　efficient　computer-aided　design　tool　of　ellipse　gears　whose　application　occupies　absolute　majority　part　in　the　field　of　non-circular　gears.