Referring to the technology of SAW wireless identification systems, a multi-resolution wireless force sensing system, including a passive time-delay SAW device and a specific interrogation unit, is introduced in this paper. Using an IDT, which connects with an antenna, as the force sensing element is a design to transduce the electromagnetic wave into surface acoustic wave and vice versa. Several reflectors are designed to get multi-resolution. Sample/hold devices are used instead of high-speed A/D converter to construct a low-cost interrogation system. Properties of the sensing system are theoretically predicted and experimentally verified.