A coronal index (CI) derived from the limb observations of the 530.3 nm emission corona (green corona) over 1964–1987 was analyzed by the Fourier transform technique (FTT) to find periodicity in this layer of solar atmosphere. As expected, two pronounced periods were indicated: the rotational, about 27 d, and the activity cycle length, 11 years. Beside these there are seen other periodicities of less significancies, namely of about 5,2.2,1 and 0.5 year. The values of these periodicities in individual cycles 20 and 21 slightly differs that could be related to different activity zone depths beneath the photosphere.