Abstract: Seedling culture in nutrient solution without substrate is a new seedling technology for vegetables. As the plants are grown in nutrient solution for the entire seedling stage, how to control excessive growth and how to cultivate strong seedlings are the problems to be solved, especially in summer. To study the effect of chlormequat chloride (CCC) on inhibition of spindling and cultivation of sound seedlings with cucumber in summer, different concentrations (5, 10, 15 mg/kg) of CCC were added in nutrient solution. The results showed that adding CCC in nutrient solution could apparently reduce hypocotyl length, plant height as well as internode length. With CCC treatment, the color of leaves became greener, the ratio of root to shoot was higher. Compared to the control, the seedling index of 5, 10, 15 mg/kg treatments increased by 27.3%, 45.5% and 15.2%, respectively. This suggested that adding CCC in nutrient solution could inhibit seedling spindling and the biomass accumulation in aerial parts, and promote the growth of underground part, which was beneficial to formation of strong seedling. Among the three treatments, adding 10 mg/kg CCC in nutrient solution had the best effect on inhibition of the excessive growth and cultivation of strong seedling with cucumber in summer.