This paper reports a low-power transceiver with a reconfigurable sliding-IF (intermediate frequency) architecture used for wireless body area networks hubs covering multiple frequency bands (400, 900 and 2400 MHz). By using this architecture, a 1600-2000 MHz phase-locked-loop (PLL) synthesizer with only 25% tuning range can fully cover these three bands. The multi-band Transceiver has been designed in 0.18 um CMOS process. The design consists of a receiver with wideband front-end and reconfigurable amplifier-mixer, a transmitter with reconfigurable two stage full quadrature mixer,a SD fractional-N PLL and some assistant circuits. The measurement result has demonstrated that the designed transceiver can satisfy the multi-band requirements with comparable or even better performance in noise, linearity, receiver sensitivity and power consumption compared to previously-reported single band transceivers.