This article proposes a novel antenna structure by slot loading method based on the planar inverted F antenna (PIFA), which is fed by coaxial probe. The antenna structure consists of a new and flexible slot array including five slots. To reveal the mechanism of slot loading in creating new and broad frequency band, the article discusses the performance of the five slots in detail. Simulations with Ansoft HFSS 10.0 indicate that the -10 dB relative impedance bandwidth can reach 17.2%, 8.9% and 12.1 % that covers 2.40/3.30/5.15/5.725 GHz wireless local area network (WLAN) and world interoperability for microwave access (WiMAX) bands. Meanwhile, the antenna has stable radiation pattern, high gain and low profile. Especially, the slot array is flexible and capable of being realized in various application cases. Actually the design reaches broadband, multi-band, miniaturization, high gain and is easy to fabricate.