The invention relates to a composite growth regulator for increasing yield and saccharinity during the sugar accumulating period of beetroot and a usage, which are particularly suitable for the application under the arid environment, and have obvious effect on increasing yield and saccharinity through the foliage spray in late August. The regulator can not only control the injury caused by the stress of the environment, and keep the duration of the function foliage at the maximum, but also increase the activity of sucrose synthase, reduce the consumption of glycogen, promote coordination and uniform of the beetroot and the environment, individual and group, root and overground part, the external shape of the plant and internal physiological function during the sugar accumulating period, and finally reach the goal of improving the yield and saccharinity. Under the environment of the west of Jilin province, with less than 300 mm of the amount of precipitation, 0.47 percent of salt content and PH value of 8.6, the yield of beetroot reaches to 52,766.25kg/hm2, the yield is increased by 12.18 percent, and the sugar content is 17.0 percent, which is increased by 1.4 percent.