Abstract: The empirical orthogonal function (EOF) is analysed with rain field in summer of Hunan from 1958 to 1995.The resultes show EOF can mirror the features of spatial distribution of the precipitation field.Assigning the rain field in two section,from 1958 to 1983 and from 1970 to 1995.the stability of EOF on the three field are compared and discussed.It is shown EOF is stability under given conditions.Then the alignment stretches right to 1997,assigning the field two section of not crisscross,or from 1958 to 1977 and 1978 to 1997,the show EOF is stability yet.The cause possible relate to the difference is nor greatly in levels of average correlation within the fields.On the basis of above-mentioned analysis,long-range forecast of rain filed is maked using a modelling scheme of screening of chief component.