Abstract: Carbon nanotube （CNT） field-emission cold cathodes exhibit several intrinsic advantages, including room-temperature operation, rapid pulse response, low power consumption, and compatibility with compact device architectures, and are therefore regarded as the promising electron source for high-performance miniaturized X-ray tubes and other vacuum electric devices. However, their practical implementations are still limited by issues such as insufficient emission stability, nonuniform current distribution, and the difficulty of efficiently transporting and focusing high-current electron beams within a compact electron-optical system. In this study, multi-walled CNT films were directly grown on nickel-alloy substrates by chemical vapor deposition （CVD） to construct an integrated field-emission cathode. The emission characteristics were systematically evaluated using a diode configuration, and the field-emission behavior was analyzed on the basis of the Fowler–Nordheim model. A triode electron gun consisting of the CNT cathode, extraction grid, and focusing electrode was further designed and optimized through particle-tracking simulations, with particular attentions to the electron transmission, beam compression, and focal-spot control. The corresponding X-ray source was subsequently assembled and experimentally characterized. This cathode was able to deliver a high emission current density of 1.8 A/cm² at the applied electric field of 10 V/μm, demonstrating its capability for high-current operation. After electron-optical optimization, the electron beam was compressed by a factor of 4.3, while the X-ray tube reached a tube current of approximately 2 mA and an electron transmission efficiency of about 70%. X-ray imaging experiments using a line-pair test pattern confirmed a spatial resolution of better than 100 μm. In addition, the pulsed grid control mode enabled a tube current of up to 3.2 mA, and the stable operation was maintained for 8 h under continuous testing mode. These results demonstrated that the combination of directly grown CNT cathodes and optimized triode electron optics can simultaneously improve the emission capability, beam transport efficiency, and operational stability, thereby providing a practical technical approach for the development and engineering applications of compact CNT cold-cathode X-ray sources.