A novel passive bio-sensing method, which electrically connects a conventional biosensor to a surface acoustic wave (SAW) device, is proposed for passively sensing bio-impedance for zero-power wearable applications. The biosensor attached to the SAW as the load of the tag (the SAW acting as the loadable reflector), makes the measuring of the biosensor fully passive without power supplied to sensor side, being suitable for power restricted applications. Simulations showed that the paramagnetic particle enhanced biosensor has a better measurement accuracy than that of an ordinary biosensor. The feasibility of this new biosensor has been demonstrated by the preliminary experiment of using a 50ns pulse train containing RF signal to excite the new device, which is implemented by a 3.5 mm diameter coil-shaped electrode of a biosensor connected to a 433MHz single port SAW resonator, and then to collect and analyze the reflected signal. This passive solution of getting bio-impedance information using a SAW connected conventional biosensor, enables massive production of the impedance loaded SAW biosensors.