With the rapid employment of LTE in mobile broadband services, the requirements of broad bandwidth for mobile terminals, such as tablet computer, are increasingly urgent. A miniaturized multi-band antenna(15 mm×40 mm×0.8 mm) employed in LTE/GSM/UMTS is designed, which can be applied to tablet computers. A T-shaped driven monopole structure is introduced in order to reduce the effective height of PIFA(Planar Inverted F-shaped Antenna) used in ultra-thin tablet computer. The low band(850 MHz-910 MHz) is extended by embedding a parallel-resonant spiral inductor. The high band(1 710 MHz-2 690 MHz) is extended by loading a Defected Ground Structure. The antenna covers the bandwidth of GSM850/900/1800/1900/ UMT2100/LTE2300/2500, and the gain of the antenna also meets the basic requirements of a tablet computer.