The invention provides a snapshot type optical field-polarization imager and an imaging method thereof. An objective lens, a field diaphragm, a collimator lens, a micro lens array I, a wave plate array, a polaroid array, a micro lens array II, a photoelectric detector, and a signal processing part are arranged successively along a light direction. Light from a target is collected to the field diaphragm by the objective lens and the collected light reaches the micro lens array I by the collimator lens; the light passes through the wave plate array and the polaroid array and a series of sub images are generated at a rear focal plane of the micro lens array I; and the sub images are imaged on the photoelectric detector and the signal processing part through the micro lens array II. In addition, according to the imaging method, target image and depth reconstruction are carried out respective in the sub areas with different wavelengths and then polarization is calculated. According to the invention, the image, polarization and depth four-dimensional information of the target can be obtained within primary integral time of the detector; and average processing is carried out on the targetdepths of all wavebands, so that the precision of the target depth is improved substantially.