To realize high-precision and high-efficiency measurements of the geometric dimensions of inertial confinement fusion (ICF) capsules, an X-ray digital imaging system applied to characterize the geometric dimensions of capsules was designed and developed. First, the X-ray direct-projection imaging and X-ray lens coupled microimaging were theoretically analyzed and a technical approach based on X-ray lens coupled microimaging was chosen due to its small size and the weak-absorption contrast of ICF capsules. Then, the key factors affecting the imaging resolution, image contrast, and measurement efficiency of the system were analyzed. A technical scheme of low geometric magnification imaging, a low voltage X-ray source, a small focus, and high power and high-resolution charge-coupled device (CCD) detection was determined. Utilizing this scheme, the phase-contrast effect and penumbra error can be suppressed effectively and the problems of serious edge expansion and large measurement error, which exist in X-ray digital imaging equipment used to measure the capsules, can be solved. Finally, the system performances were tested and the experimental results illustrate that the system has an excellent imaging contrast, high efficiency, and high resolution better than 0.5 μm. The measurement uncertainty of the geometric dimensions of ICF capsules is approximately 0.9 μm (k=2), meeting the high-precision and high-efficiency measurement needs of ICF capsules.