With the construction of new power systems, complex operating conditions have raised higher requirements for the state perception and operation maintenance of power equipment. Regarding the partial discharge (PD) measurement test currently used for quality control, GB/T 7354–2018 stipulated that, after completing the charge quantity calibration, the test was considered to be passed and the equipment could be delivered or put into operation if the apparent charges meet the requirements, even if there were single or multiple PD sources generating low amplitude pulses. In this paper, The ultra-wide-band PD detection was proposed to record the partial discharge pulse sequences as an optional supplement to quality control tests. The design schemes of an ultra-wide-band PD measurement instrument formed by the multi-channel acquisition and storage device, the transmission system, and the terminal software were introduced, and the PD and noise source separation technology was described in detail, which was the core module of the terminal software and realized the pulse acquisition and storage, pulse filtering, pulse feature extraction and pulse clustering analysis. Finally, an ultra-wide-band PD measurement instrument with a sampling rate of 250 MS/s and a bandwidth of 10 kH–50 MHz was developed and its application on power transformer diagnosis was presented.