Abstract: Cultivation of sugar beet in the central and southern parts of our country is a new thing during the Proletarian Cultural Revolution and is one of the most promising ways for developing our sugar production. In Yountze River area, it is practicable to grow sugar beet in the autumn, over- winter in the field and harvest in the next spring for the purpose of avoiding seasonal competition with cereal crops. In general, however, overwintered beet plants always bolt and have to be harvested before the beginning of April, because bolting cuts down sugar content significantly and also make processing difficult due to lignification of the roots. Inhibition of bolting may result in extension of growth period of the crop so that higher yield of root and sugar can be obtained. According to the results of experiments carried out in the last three years in Shanghai, Kiangsu, Chekiang and Hunan, it has been proved that bolting of overwintered autumn sown sugar beet can be effectively retarded by foliar application of maleic hydrazide at the concentration of about 0.3%, 7–10 days before bolting. With this method, the harvest time can be delayed about one month. Examination of the actual benefit of this method was made for the first time in the field of Miloo River Farm of Hunan province in this spring. Harvest time was delayed 24 days with MH treatment. The yield of beet roots per mu and total content of sugar per mu calculated according to the sugar content of the beet roots at the harvest time, are both increased remarkably as compared with that of the control. Residue of MH in the beet roots, determined one month after treatment with 0.4% MH solution, is onty 1.7 ppm. It is reasonable to suppose that the residue of MH in sugar should be negligible.