Abstract: Mustmelon was used as experimental material.The root application method was carried out.The mixed solution of 100 mmol·L^-1 NaCl and NaHCO₃ was used to simulate saline alkali environment in this study.Different concentrations of fulvic acid（FA） were used as exogenous regulator, seven levels of FA concentration were set, which were 0（CK1）,100 mg · L^-1（T1）,200 mg · L^-1（T2）,400 mg · L^-1（T3）,800 mg · L^-1（T4）,1 600 mg · L^-1（T5） and 3 200 mg · L^-1（T6）.The effects of fulvic acid on morphology, biomass, chlorophyll and root development of muskmelon seedlings under saline alkali stress were studied, in order to provide reference for alleviating crop growth by root application under saline alkali conditions.The results showed that, the saline alkali stress was alleviated with the increase of fulvic acid concentration on muskmelon seedling.The biomass, net photosynthetic rate and root activity of muskmelon seedlings increased first and then decreased.As compared with CK1,the total dry weight of melon seedlings in T3 treatment increased by 23.0%.As compared with CK1,the underground dry weight of T3 and T4 treatments increased by 27.0% and 38.0%,respectively.As compared with CK1,the total chlorophyll content of melon seedlings in T4 treatment increased by 47.1%,and the root dry matter accumulation of melon seedlings was significantly higher than that of CK1 with the increase of fulvic acid concentration.The root activity of muskmelon seedlings grown under CK3 and CK4 treatments were significantly higher than those of CK1.Therefore, the application of fulvic acid in the range of 400-800 mg·L^-1 could significantly alleviate the growth of muskmelon seedlings under 100 mmol·L^-1 saline alkali stress.