The non-destructive testing of cultural relics has great significance for the protection of cultural relics and can provide a strong basis for subsequent reinforcement and protection. In view of the shortcomings of the traditional ultrasonic testing equipment with small gain and low echo signal characteristics, it is difficult to meet the defect detection of stone or wooden relics. An ultrasonic nondestructive testing system for stone or wood materials based on FPGA as the main controller is designed, and the characteristics of echo signal are analyzed in detail. The hardware part of the system includes the excitation of ultrasonic signal, the amplification of the echo signal, the design of the filter and sampling module. The software part includes the logic design of FPGA and the software design of the USB communication. At the same time, the acquired echo signal is analyzed, including the time domain analysis, frequency domain analysis and wavelet analysis, and the characteristics of the echo signal are obtained, which lays the foundation for the ultrasonic nondestructive testing of the stone wood materials.