The invention discloses a snapshot imaging spectrometer based on a stepped phase reflector and a manufacturing method, and relates to the technical field of infrared imaging spectrum detectors, and solves a problem of the real-time obtaining of a three-dimensional data cube in a conventional imaging spectrometer and a problem of miniaturization of the imaging spectrometer. The imaging spectrometercomprises a collimating mirror, a micro-imaging mirror array, a beam splitter, a lateral stepped phase reflector, a longitudinal stepped phase reflector, a relay imaging mirror and an area array detector. The imaging spectrometer employs the micro-imaging mirror array for the multiple imaging of a target scene, and employs the stepped phase reflectors for the distributed phase modulation of a multi-image field. Through the optical field coupling of a parallel imaging channel formed by the micro-imaging mirror array and a parallel interference channel formed by the stepped phase reflectors, the imaging spectrometer achieves the multi-channel snapshot interference imaging of the target scene, does not need a complex motion mechanism, is miniature, is static, is high in stability, is high inintegration degree, and is high in detection speed.