The invention discloses a GPS-based bundling machine bale yield measuring device, which comprises a measuring assembly and a measuring system used for processing measure data, wherein measuring assembly comprises two discharging detection plates which are arranged in parallel; two pairs of positioning frames are mounted on each of the two discharging detection plates; four positioning sliding strips are connected to the two pairs of positioning frames jointly in a sliding manner; a displacement sensor and a displacement reference plate for receiving a detection signal of the displacement sensor are mounted on the two discharging detection plates respectively; a transparent protective cover is arranged outside the displacement sensor; a probe of the displacement sensor is level with the bottom surface of the discharging detection plate on the upper side; and the displacement reference plate is level with the upper surface of the discharging detection plate on the lower side. The invention further provides a GPS-based bundling machine bale yield measuring method. the GPS-based bundling machine bale yield measuring device and the GPS-based bundling machine bale yield measuring methodare reasonable in design, solve the problem that the manual measuring and calculating process is tedious, and greatly improves the precision and efficiency of bale yield measurement.