This experiment was conducted by drenching the substrate with varied concentrations of chlormequatchloride（200mg/L, 300mg/L, 400mg/L, 500mg/L and 600mg/L） before sowing to study their effects on the quality ofcucumber plug seedlings. The results demonstrated that the cucumber seedlings treated with 400 mg/L chlormequatchloride showed good results in terms of the plant height, hypocotyl length, stem diameter, root vigor, chlorophyllcontent and soluble sugar content of cucumber seedlings, which were better than seedlings treated with 300 mg/Lchlormequat chloride. It could therefore be concluded that drenching the substrate with 300~400 mg/L chlorme-quat chloride could help avoid excessive seedling growth and cultivate strong seedlings.