1. A method of determining a whole-scene image by using multiple image-capturing devices, comprising: (a) arbitrarily selecting a first image-capturing device, a second image-capturing device and a third image-capturing device located in a whole-scene space; (b) determining a first base line, a second base line and a third base line on a basis of the second image-capturing device; (c) calculating coordinates of the first image-capturing device, the second image-capturing device and third image-capturing device; (d) performing a fitting calculation for a co-circle according to the coordinates; (e) calculating a cyclic point and a radius of the co-circle, and a first angle θ 1 and a second angle θ 2 ; (f) when a number of the image-capturing devices exceeds three, selecting the at least one of the first, second and third image-capturing devices, and two image-capturing devices comprising one image-capturing device other than the first, second and third image-capturing devices, and defining the selected three image-capturing devices as the first, second and third image-capturing devices in the step (a) and then performing the step (a) through step (h) according to the selected three image-capturing devices; (g) calculating a con-cyclic plane of the co-circle, and arranging the first, the second and the third image-capturing devices according to the con-cyclic plane; (h) analyzing images captured by the first, the second and the third image-capturing devices to determine whether an image calibration is required; (i) according to the con-cyclic plane, evaluating a correlation between a single circle and the con-cyclic plane joined with each other, so as to obtain a physical quantity analysis result of the whole-scene after analysis of a correlation evaluation report; and (j) determining the whole-scene image according to the physical quantity analysis result.