对于太赫兹微电真空折叠波导行波管 (FWG-TWT)放大器，高流通率是试验测试中首先需要达到的技术指标，是器件连续工作时高效束.波互作用的前提。电子光学系统包括电子枪、周期永磁聚焦系统 (PPM)和收集极。本文通过对电子枪的高品质束流的产生、 PPM对束流的聚焦 2个方面研究束流的直流流通率。首先依据 Vaughan迭代综合法初步选定电子枪的基本结构尺寸，然后通过粒子跟踪程序及PIC程序对电子枪的结构参数进行仿真优化，初步实现了 0.345 THz FWG-TWT放大器所需的束流品质；进行了电子光学系统的电子枪和 PPM的一体化数值模拟，研究了电子的直流流通率，最终流通率模拟结果达到 100%。

High passing rate of the beam is one of the most essential technical targets for terahertz micro-electric vacuum Folded Waveguide Traveling Wave Tube(FWG-TWT) amplifiers, which can guarantee highly efficient continuous beam-wave interaction. The optical system is composed of electron gun, Periodic Permanent Magnet(PPM) and collector. The paper will focus on the gun which is used to produce the electron beam and the PPM which is used to focus the beam, to study the direct current passing rate of beams. Firstly, the sizes of the gun’s structure are initially determined by using Vaughan iterative method, and then particle tracking code and Particle In Cell(PIC) code are applied to optimize these structure parameters. The beam of high quality required for 0.345 THz FWG-TWT amplifiers is realized. Numerical simulations of the whole integrated optical system are carried out to study the direct current passing rate of beam, and it reaches 100% ultimately.