The invention provides an endoscope system and a motion control method thereof, and a processor device therefore, even if the difference of oxygen states of blood vessels is very small, the difference can be identified to be color difference being displayed a test body is illuminated by narrow band light of a first different absorb waveband with oxyhemoglobin having a bigger light absorption factor than reduced hemoglobin having a smaller light absorption factor, and the test body is videoed to obtain blue image data Bx. The test body, illuminated by G light having green waveband, is videoed to obtain green image data Gy intensity ratio B/G is calculated according to the blue image data Bx and the green image data Gy the intensity ratio B/G and the reduction of the oxygen saturation correspondingly enlarges gain processing corresponding to the intensity ratio B/G is carried out for the blue image data Bx and the green image data Gy, thereby obtaining blue image data Bx* and green image data Gy*. And oxygen saturation image can be displayed according to the blue image data Bx* and green image data Gy*.
