In high-energy density physics (HEDP) experiments, accurate diagnostics of physical parameters such as electron temperature, plasma density, and ionization state are essential for understanding matter behavior under extreme conditions. X-ray spectroscopic techniques, particularly those employing crystal spectrometers, are widely used to achieve high spectral resolution in these scenarios. However, a common challenge in such experiments lies in the inherently low brightness and poor spatial coherence of laboratory-based X-ray sources, which limit photon throughput and, consequently, diagnostic accuracy. Enhancing the efficiency of X-ray optical transport between the source and the detector is therefore a critical step toward improving overall system performance.Capillary X-ray optics, which function based on the principle of total internal reflection within hollow glass structures, offer promising avenues for beam shaping, collimation, and focusing in the soft to hard X-ray range. These optical devices are typically categorized into polycapillary and monocapillary types. While polycapillary optics are composed of numerous micro-channels and used primarily for collimating or focusing divergent X-rays, monocapillary lenses—consisting of single curved channels—offer more precise beam control and are particularly suited for customized X-ray pathways. Depending on the curvature of the inner reflective surface, monocapillaries are classified into conical, parabolic, and ellipsoidal geometries. In this study, we propose and analyze a novel design of a large-caliber conical glass tube, specifically tailored to address the issue of low light utilization in multi-channel Focusing Spectrographs with Spatial Resolution (FSSR). The proposed conical glass tube, fabricated from a single large-diameter capillary structure, simplifies alignment requirements and reduces the surface manufacturing precision typically demanded by complex aspheric lenses. Its geometric configuration enables the redirection and controlled convergence of X-rays from extended or weak sources, thereby improving photon collection without significantly altering beam divergence.To quantify the performance of this optical system, we developed a detailed mathematical ray-tracing model and implemented it in MATLAB. The model incorporates physical parameters such as capillary inner radius, taper angle, reflection losses, and source-detector geometry. Numerical simulations reveal that the new conical design achieves a 3.1-fold improvement in source utilization efficiency compared to conventional flat or slit-based systems. Furthermore, the lens exhibits a ring-shaped enhancement region in the output intensity profile, which is tunable by adjusting the capillary geometry and source positioning. This feature enables the spatial tailoring of the beam profile, facilitating optimized coupling with downstream spectroscopic components or imaging systems.In conclusion, the proposed large-aperture conical monocapillary X-ray lens provides a practical and efficient solution for enhancing X-ray optical transport in low-brightness source environments. Its simple construction, tunable focusing characteristics, and compatibility with diverse X-ray source types make it a compelling candidate for integration into high-resolution X-ray diagnostic systems, particularly in HEDP and laboratory-scale X-ray spectroscopy. This work not only introduces a novel optical approach but also offers a robust theoretical and simulation framework that can guide future experimental design and application of capillary-based X-ray optics.