Based on a cross spectral analysis, the relationship between the periodic fluctuation of the accumulated temperature (∑T) during May to Sept. and corn yield (Y) is obtained, and the distribution features of the power spectra are discussed. The results show that there is a 3.3-year period of ET fluctuation in Liaoning and Jiling Provinces, and a 2.5-year one in Heilongjiang Province, a 6.68-, 4.0- and 4.0-year one of Y fluctuation in Liaoning, Jilin and Heilongjiang Province respectively.