The invention discloses a method for forecasting retention time of gas chromatography under temperature programming after shortening of a chromatographic column. The method includes the steps: firstly, determining dead time and capacity factors corresponding to optional temperature points of an original chromatographic column and correcting the number of column plates of the shortened chromatographic column by using benzene as a standard substance; secondly, forecasting the retention time of components in the shortened chromatographic column under temperature programming; thirdly, measuring the retention time of the components in the shortened chromatographic column according to the determined temperature programming in the forecasting step; and fourthly, computing the relative deviation of the forecasted retention time of the components, and judging that forecasting precision meets requirements when the absolute value of the relative deviation is smaller than 2%. The method has the advantages that experimental cost is saved, the working intensity of analysis is reduced, practical ways are provided for selecting optimal separation conditions of the gas chromatography of the short column, the forecasting process is clear, and the method is applicable to wide-range popularization and application.