An optical system for short wave infrared imaging spectrometer was proposed based on prism-grating-prism(PGP)component. The system is composed by off-axis TMA, collimator, PGP and re-imaging lens, and its response covers the range 950 to 2 500 nm with a 22.5°field of view. The system is able to achieve wide field and broadband. By optimizing the PGP paramters and tilting the reimaging lens along the spectral dimenstion, keystone and smile became slight and were even less than 5 micrometer. Thus the obtained spectral data were more exact.