Abstract:The properties of the impregnating varnish are introduced and the status of the epoxy resin insulating varnish, unsaturated polyester insulating varnish, diphenyl ether resin insulating varnish, polyesterimide insulating varnish, polyimide insulating varnish and organic silicon insulating varnish are explained. The developing trend of insulating impregnating varnish is prospected.