A large aperture optical system near-field detection device and a measuring method thereof are provided; a collimating mirror, a microlens array and a detector form a Shack-Hartmann Wave-front measuring device; the features are that a spot light source array is arranged in front of a measured object to serve as a measuring beacon; a spectroscope and a scaling spot light source are arranged in front of the focal point of the measured object; the collimating mirror, the microlens array and the detector are arranged in order behind the focal point; the spot light source array, the measured object, the spectroscope and the scaling spot light source form a system self-check optical path; the spot light source array, the measured object, the spectroscope, the collimating mirror, the microlens array and the detector form the measuring optical path. The method uses the correlation of the third-order aberration in an entrance pupil position as the theory basis, uses the near field spot light source array as the measuring beacon, thus realizing large aperture optical system near-field detection; the method and device can be widely applied to detection of large optical systems under indoor and beacon-free conditions.