The spectrum analysis and factor analysis are employed in this paper for the mon-nthly rainfall days in 46 stations over China.The results of the spectrum analysis show that the first wave in the harmonic waves is preponderate in the harmonic waves, the significant areas are North, Northeast, South-west and South of Chain, and the maxium values of amplitude occure in July and August.The first six principal components, which is from the amplitude matrix of the first harmonic wave, have been rotated with maxium variance rotated technique, which have the meaningful characters corresponding to some areas in China. Their variety features with time have the increasing tendency year by year, and the periodic fluctuation with quasi-biennial and 22-year.