In this paper, a planar polarization diversity antenna with low correlation coefficient and low mutual coupling is developed for wireless sensor network system at UHF region. A slit, to eliminate mutual coupling between two antennas, inserted on ground plane of conventional diversity antenna is straight; this fact causes a restriction to layout of a PCB board at UHF region. To save a large area for the electric component, we employ an Lshaped slit which has an advantage of compact and same performance as straight slit. The prototype of diversity antenna has been developed and measured. The measured result obtained the very low correlation coefficient of 0.021 and very low mutual coupling about -20 dB at 1 GHz in this work.