This invention relates to an inverse-F antenna and its preparation method, in which, the antenna includes a radiation part, an earth part and a connecting part connecting them, the radiation frequency is at the bands of 900MHz and 1800MHz, the processing method includes: 1, selecting a rectangular metal plate, 2, determining the length of the antenna radiation part according to the working bands 900 and 1800MHz of the antenna, 3, determining the height and shape of the connecting part based on the impedance match necessary for the antenna, 4, opening recesses on the metal plate based on said computing result to get a radiation part, a connecting part and an earth part based on the computed result, 5, determining feeding points based on impedance match and providing feed lines electrically connected at the feed points.