Multichannel pulse amplitude analyzer is the core part of ray energy spectrum analysis system. In order to meet the requirements of ultra-low power consumption and portable high accuracy of the instrument, this design is characterized by the application of differential circuit in the screening circuit, which eliminates the analog switch, capacitance and diode, and greatly reduces the power consumption of the instrument. Without the use of diodes, circuits can discriminate pulses of any magnitude, especially in gamma-ray spectrometer systems. The overall structure is 89C52 MCU as the control core, simple design, external RAM storage measurement data, through RS-232 serial port and computer communication. According to the requirements of the measured frequency, switching values of R and C can be applied to a variety of energy spectrum analyzer systems.