Control systems were designed for cryogenic distillation columns in the main fuel cycle and the breeder blanket interface systems of fusion reactors. Three basic control modes were proposed for the column whose top product was more important; the column whose bottom product is more important; and the column having a feed back stream. The key component in the important product stream was selected for each column, and the analysis method for measurement of this key component was discussed. Some of the columns need the gas chromatography as the analysis instrument of the control system. The time required for the measurement of product purity by the gas chromatography considerably affects the stability of the control system. A significant conclusion is that permissible time is about 20 min. It is possible to complete the measurement within 20 minute by the gas chromatography. The gas chromatography is applicable for the control system of the column. (author).