As traditional grating-based spectrometers can not offer fast apertures and small volume systems synchronously, this paper designs a convex grating by using holography and develops an imaging spectrometer with the convex grating as a core element. It acquires the image of target by pushbroom scanning, then obtains the data cubes of the imaging spectra. The image spectrometer has a space resolution of 2.4 nm, a spectral line bend of 0.1%, the chromatic distortion of 0.6%, and a volume of 209 mm×199 mm×110 mm. The principle of imaging spectrometer with convex grating is analyzed and its constructs are described. Then, a spectral experiment in the laboratory is carried out and the spectra of extraventricular flowers are tested. The result demonstrates that the real spectral resolution is 2.1 nm, line bend is 0.09% and the chromatic distortion is 0.6%. These data satisfy the design requirement, and obtained spectra are ideal results.