The signal output by a nuclear radiation detector is small in amplitude and irregular in waveform, which needs to be amplified and shaped to measure accurately. Spectrometer amplifiers assume the role of signal amplification and shaping in nuclear radiation measurement instruments, strictly maintaining useful information from the detector output (such as energy information and time information of the rays) and minimizing their distortion during signal processing. According to the needs of undergraduate experimental teaching and nuclear instrument development and application of nuclear electronics courses in nuclear science and technology, this paper designs a flexibly switchable pole zero phase extinction circuit, linear pulse amplification circuit, integral filter forming circuit, and baseline restoration circuit in the experimental circuit board of spectrometer amplifier. The total magnification is about 0 ~ 2040 times adjustable, and the forming time is 0~20μs adjustable. It has the functions of limiting voltage amplitude and optional input and output polarity, which can be adapted to scintillator detectors, proportional counters, Si-PIN, SDD, HpGe and other semiconductor detectors.