This article uses eight 10 GSps ADCs to design an ultra-wideband high-speed data acquisition (DAQ) system with 80 GSps and 20 GHz bandwidth based on the bandwidth-interleaved (BI) sampling architecture and applies it to a real-time digital storage oscilloscope (DSO). Research is implemented on sub-band decomposition, acquisition synchronization between multiple sub-bands, overlapping bands, and full-band splicing. Based on the divide and conquer method, corresponding calibration and compensation methods are proposed. The comparative analysis is conducted within both the time and frequency domains, prior to and subsequent to the implementation of the compensation technique, and substantiates the efficacy of the proposed method. The findings from the experiment show that the DAQ system attains a sampling rate of 80 GSps and a bandwidth of 20 GHz. The system ENOB and SFDR could reach 6 bits and 40 dB at 20 GHz, and the changing curve of ENOB with frequency is given. The rise time of the acquisition system is 22 ps. Experimental data show that the system’s various indicators are at the leading domestic level.