Abstract: Resistance spot welding quality real-time monitoring of aluminum alloy was realized by distributed multiple-sensor synchronous collection system. Displacement signal time-frequency domain analysis shows that Butterworth band-pass filter range of the expulsion welding spot electrode displacement signal can reach about 0.5 mm between 40-80 Hz. The electrode displacement signal range of the undersize welding spots is lower about 1.0 mm than other two kinds of welding spots, so that using the explicit characteristic information can implement at resistance spot welding quality judgment by man and further can finish quality judgment by machine using the high signal-to-noise displacement signal and the brevity characteristic extracting method. At the same time, statistic analysis of 197 samples indicates that the percentage of accuracy can reach 97.6% at the acceptable welding spots zone.