A reconfigurable CMOS mixer for multi-standard application is presented. The mixer can be tuned and adjusted to multi-frequency bands using a flexible matching network which is a kind of variable reactance transformer. The flexible matching network consists of a few switched inductors and capacitors. The mixer has acceptable conversion gain, IIP3 and NF. It operates with a return loss of less than - 10 dB through 2-6 GHz except for a few narrow frequency bands.