Hyperspectral imager can obtain both spatial information and spectral information at the same time, which is widely used in agriculture, biomedicine, environment monitoring. At present, hyperspectral imager is developing in the direction of lightweight, miniaturization and low power consumption. The miniaturization of hyperspectral imager includes the miniaturization of optical system and the miniaturization of detector system. In this paper, a miniaturization hyperspectral imager based on CMOS detector is proposed. The working range of is 400-1000nm, which contains 512 spectral bands. The field angle of hyperspectral imager is ±4 degree and the focal length is 99mm. The optical system consists of the telescope, the slit and the spectrometer. Considering the miniaturization of optical system, the spectrometer uses prism-grating spectroscopy. The CMOS sensor GSENSE400BSI is used in the detector system, whose pixel size is 11 micron*11 micron and pixel number is 2048*2048.The detector system consists of an imaging core board and an interface board, and the image output is Cameralink interface. Because of the high integration of CMOS sensor, the design of peripheral circuit can be greatly simplified. The total weight of the hyperspectral imager is not more than 2.5kg and the total power consumption is not more than 5W.The spectral imaging system has the advantages of lightweight, miniaturization and low power consumption. After testing, the spectrometer has good imaging quality.