This experiment was carried out by Watering the growth media with varied concentrations of Chlormequat（0 mg/L、100 mg/L、200 mg/L、300 mg/L、400 mg/L、500 mg/L） before sowing. The results showed that the higher the concentration of chlormequat, the stronger the dwarfing effect. The plant height and hypocotyl length of tomato seedling were effectively controlled when the concentration of cabbage was 200 mg/L, and the strong seedling index, root/shoot ratio, chlorophyll content and peroxidase activity of the seedlings meet with standards, seedlings performed well. Therefore, it is recommended to use 200 mg/L of chlormequat solution at the bottom of the seedling culture substrate before sowing, which effectively control the tomato seedlings leggy and achieve the purpose of strong seedlings.