The present invention discloses a dual-band active filter having filtering response and positive pass-band gain. The dual-band active filter includes an input match unit for gain match of the dual-band active filter and for having a band-pass filtering response; a first gain stage electrically connected to the first input match unit for providing the flat gain of the dual-band active filter; an inter-stage unit electrically connected to the first gain stage for matching gain and for having a band-stop filter response; a second gain stage electrically connected to the inter stage unit for providing the flat gain of the dual-band active filter; and an output unit electrically connected to the second gain stage for matching the dual-band active filter and for having a low-pass filtering response. The dual-band active filter according to the present invention uses the cascade connection of multiple filter stages to have band-pass filtering response at two different frequency bands and obtain high stop-band attenuation by providing plural transmission zeros in the stop-band.