Abstract: A digital gamma ray spectrometer based on 80 MHz ADC was presented. The system consists of NaI(Tl) detector, front-end circuitry, 80 MHz ADC and digital pulse process (DPP) unit. The FIR digital filtering, pulse trapezoidal shaping, pulse height discrimination and data communication were implemented in DPP. The pulse trapezoidal shaping algorithm was applied to obtain good energy resolution and throughout. In order to reduce the influence of noise introducing from the high-speed ADC, the FIR digital filter was employed. The digital signal coming from ADC was smoothed by FIR filter firstly, and then shaped as trapezoidal pulse for further processing. The analog signal was coupled by DC, and the digital pulse width is 1.6 μs. The results show that the resolution for ¹³⁷Cs can reach 6.88%.