In this paper the midium and short periodic fluctuations of meteorological components related to crop yield in China are discussed by means of spectrum analysis,periodogram and variance analysis. It is shown that the spectral distributions in different parts of the country are basically similar and particularly occur in a period of about 4-6 years and even twice of the period. It could be deduced that the fluctuations of agromete-orological thermal factors influence the periodic fluctuations of the meteo rological components related to crop yield and hence result in periodic variations of crop yield.