Combined with pulsed interrogation principle of resonant SAW wireless sensor system, based on the reader hardware system, the two main sources of error, which are local oscillator phase noise and ADC error are studied. The effects of the two main source errors on the system measurement uncertainty have been analyzed respectively, and each component has been synthesized.Quantitative analysis can be used as a guide to choose appropriate parameters and improve the system hardware design, and the measurement performance can be enhanced greatly.