In space target observation missions, there is a need for highly sensitive target detection and high-quality imaging. However, there is a significant disparity in the field of view between detection and imaging, and currently, two primary solutions are predominantly employed. One approach involves the design of two independent subsystems, while the other method utilizes a shared-aperture dual-channel design to integrate the functions of detection and imaging into a single system. However, designing two independent systems necessitates a substantial amount of space to accommodate these two subsystems, often exceeding the carrying capacity of most existing space optical payloads. On the other hand, adopting the shared-aperture dual-channel system requires additional electronic components and structural elements, with challenges during the assembly and calibration processes. This may potentially lead to uneven energy distribution issues. In order to achieve high sensitivity detection and precise identification of space targets, this paper introduces the design of an optical system based on a continuous zoom structure that balances a large aperture with a long focal length. This system aims to achieve short focal length and wide-field target detection, as well as long focal length and narrow-field target imaging. In terms of the design methodology, the inherent complexity of the system makes it challenging to obtain an ideal structure during the optimization process. Consequently, this system combines the structures of reflective mirrors and corrective lenses with a zoom structure through optical pupil matching. It employs two reflective mirrors to compress the optical path. During the zooming process, both the zooming components and compensating components move together to maintain the position of the image plane. At the intermediate zoom position, image quality is excellent, allowing for continuous target tracking. To address the issue of uneven energy distribution within the system, this optical system utilizes a shared-aperture detection and imaging integration structure. Furthermore, with an aperture size of 280 mm, the system can detect targets as faint as magnitude 14, effectively resolving the challenges associated with detecting faint and weak targets. The system operates within the spectral range of 450 nm to 850 nm and focal lengths ranging from 700 mm to 3 500 mm. At the detection end, the focal length is 700 mm, with an F-number of 2.5 and a field of view angle of 0.5°×0.5°. At the imaging end, the focal length varies from 1 400 mm to 3 500 mm, with F-numbers ranging from 5 to 12.5 and a field of view angle of 0.18°×0.18°. At the detection end, 80% of the optical spot's encircled energy is concentrated within 17.4 μm. At the imaging end, the edge field MTF is 0.36, approaching the diffraction limit, while at the intermediate zoom position, MTF values range from 0.31 to 0.36, ensuring consistent image quality during the zooming process. This system integrates the detection and imaging systems into a single unit, achieving shared-aperture functionality. After conducting tolerance analysis on the system, it was observed that under relatively loose tolerances, MTF degradation in both the sagittal and tangential directions is minimal. Moreover, at an 80% probability, the optical spot diameter is smaller than 18.4 μm for each field of view, indicating that the system maintains excellent detection and imaging performance even under these relaxed tolerance conditions. The zoom cam curve is a critical design parameter for zoom systems, and in this system, the cam curves for both the zoom and compensator groups have an apex angle of less than 30°, meeting the design requirements. This system offers strong detection capabilities, excellent image quality, a compact overall length, and a minimal zoom cam curve apex angle. In terms of structure and design objectives, it provides valuable insights for the future development of continuous tracking integrated optical systems for the detection and imaging of targets.