Abstract: In order to achieve the automatic online ultrasonic testing for the wheel of locomotives, vehicles and EMU, a piezoelectric transmitting-receiving online testing plan was designed. A 100MHz signal sampling rate system in parallel based on the FCS was designed. The system made full use of the order sampling characteristic and use of the parallel time-division multiplexing single-channel multi-PC technology, thus improving the utilization and consistency of the high-speed A/D channel. Sampling rate could remove many redundant datas, improve the treatment efficiency of the system. And the following up defect signals dealing mode could improve the detection reliability of the qualitative and quantitative identification.