The invention discloses a high-precision identification method for an optimal excitation angle position of two-dimensional surface plasma. The method comprises the following steps: roughly positioning the position of a clear aperture circle through local binarization and Hough transform, and cutting an objective rear focal plane image acquired by an image sensor conjugated with an objective rear focal plane into a W*W square matrix image comprising the clear aperture circle; increasing a contrast ratio of clear aperture to a clear aperture external part through local binarization, and detecting the circle center and the radius of the clear aperture; counting grey value distribution in the radius direction in the clear aperture, and estimating the rough radius of a circle on which the SPR optimal excitation angle is located; determining grey distribution of pixels nearby the SPR optimal excitation angle by combining with a morphological method; and finally, calculating the circle center and the radius of the circle on which the optimal excitation angle is calculated through a least square method, thereby obtaining the precision position of the SPR optimal excitation angle.