Silicon drift detector (SDD) is a kind of high performance X-ray detector, which is widely used. The ray detection system based on SDD is composed of SDD device, preamplifier and pulse processing system. The now available pulse processing system has the problems of poor pulse pile-up rejection performance and being vulnerable to the parameter fluctuations of front-end system, which degrades the performance of detection system. A digital pulse processing system is proposed. In this system, analog-to-digital converter (ADC) directly samples the output signal of preamplifier, and transmits the data to the digital pulse processing platform for processing. According to the signal characteristics of SDD device and preamplifier, the influence of ADC sampling bits and sampling frequency on system performance is analyzed. Two optimized ADC sampling circuits are proposed to reduce energy resolution degradation induced by insufficient ADC sampling bits. The pulse shaping algorithm in the digital pulse processing system is studied. The results show that the shaping signal will not be distorted due to the parameter fluctuations of the front-end system, which proves the robustness of the digital pulse processing system. The digital pulse processing system is implemented and tested, and the correctness of the system is verified.