The invention discloses an atmospheric polarization mode detection and course calculation system and method. The system comprises two parts including a four-channel polarization image acquisition apparatus and a data processing computer, wherein the four-channel polarization image acquisition apparatus comprises a four-channel image acquisition module, an image monitoring module, a device driver and a data storage module; the four-channel image acquisition module is connected with the device driver and the data storage module through routes; and the device driver and the data storage module are connected with the image monitoring module and the data processing computer. The method comprises the steps that the data processing computer sends an instruction to the device driver and the data storage module to finish acquisition and storage work of an atmospheric polarization image; a polarization information detection module extracts a polarization degree and a polarization angle of each point from the shot atmospheric polarization image; and a course angle calculation module calculates a course angle of a carrier through the extracted polarization information. The system is simple in structure and low in cost, and processing process and result of image data are conveniently viewed.