Abstract: A new portable multi-channel automatic ultrasonic inspection system was presented. In the system, overall construction of the digital signal processing part was based on ARM platform and FPGA subsystem, and data acquisition subsystem with wide band, high gain and high speed was implemented by three gain-controlled cascaded amplifiers and high-speed ADC sampling. Combining traditional ultrasonic testing technology with some advanced technologies, such as digital signal processing, embedded Linux operation system, could meet the requirements of some key performance indexes of automatic ultrasonic inspection, such as high repetition frequency, hardware real-time alarm, and provide a very friendly man-machine interface.