Abstract: The key techniques in the development of digital storage oscilloscope (DSO), a product type project taken by the authors, are discussed, of which the concept and the theory of the system design, the high-speed data acquisition technique based on the devices with lower operation speed, the equivalent sampling technique based on Random sampling are expatiated. The 200 ps time resolution and 5 GSPS equivalent sampling rate are gotten by using large-scale time expander, so the DSO can observe 100 MHz (-3 dB) seasonal signal. The results of experiment and application are presented in the end.