In view of the measurement requirements of uniformity and areal density parameters of target metal foils, a non-destructive testing technology for high-Z metal foils by obtaining thin film X-ray transmittance and its spatial distribution through a toroidal crystal focusing type X-ray monochromatic imaging device is proposed. This technology not only effectively improves the accuracy of areal density measurement by high-throughput and high-monochromatic imaging, but also realizes high spatial resolution evaluation of thin film uniformity. This paper carries out in-depth research from the aspects of overall scheme design, component preparation and test experiment, and evaluates the influence of various possible factors on measurement uncertainty. The developed toroidal crystal imaging system achieves micro-region resolution better than 5 μm within millimeter scale for 20 keV-level high-energy X-rays, and spectral resolution reaches several eV. The feasibility of the developed technology is verified by surface density measurement experiment of foam gold sample, and relative uncertainty of areal density measurement better than 2% is obtained. This paper provides a new measurement technology for precise non-destructive testing of high-Z target materials for laser inertial confinement fusion, which is also expected to be applied to other fields that require large field of view and high spatial spectral resolution imaging.