This paper applied caterpillar-singular spectrum analysis to the analysis and long term runoff forecast of hydrologic time series.Based on the monthly runoff data from 1950 to 2007 in the Minjiang River Basin,the paper revealed the slowly varying(trend) component and oscillatory components of the runoff series through embedding step,SVD step,grouping step and diagonal averaging step of caterpillar-singular spectrum analysis.The oscillatory components of the runoff series include components with periods of 3...