The invention provides a deep-space reentry-return service platform and recoverable capsule separation attitude designing method. The method comprises the steps: according to flying attitude and attitude maneuver capacity of a separated recoverable capsule, determining reference separation attitude of a service platform and the recoverable capsule; based on the reference attitude, analyzing constraint conditions, including measurement and control conditions of the service platform and the recoverable capsule, separation safety of the service platform and the recoverable capsule, requirements of service platform star sensor reusability and the like; finally by comprehensively considering the flying attitude after separation, measurement and control conditions of a detector, power supply requirements of the detector, separation safety and requirements of the star sensor, providing a separation attitude range, which meets the requirements, of the service platform and the recoverable capsule, so that requirements of high-precision autonomous navigation, reliable separation and safety reentry requirements in a recoverable capsule reentry process are met.