Weathered coal humic acid has multiple active functional groups.To study the influence of different amounts of weathered coal humic acid on the growth and development of apple seedlings，a pot experiment was carried out.To provided a theoretical basis for the efficient utilization of weathered coal humic acid resources in increasing the production and quality of apple plant.The apple seedlings were M9T337.All the seedlings with the same growth were transplanted into the substrate pot to equilibrate for one week，and the humic acid was added at different amounts (0，0.1，0.5，1.0，1.5 and 2.0 g/kg).Their effects on apple seedling biomass，leaf enzymes，chlorophyll，substrate enzymes，substrate nutrition and other conditions were studied. The results showed that:(1)Different amounts of humic acid increased the plant height，dry weight and fresh weight of apple seedlings.Among them，the 1.5 g/kg treatment had the most obvious effects.Compared with the control group，1.5 g/kg treatment increased by 68.5%，70.6% and 53.3%，respectively.(2)Humic acid increased the content of antioxidant enzymes in leaves and reduced the content of malondialdehyde.The content of SOD，POD and CAT in apple seedlings treated with 1.5 g/kg increased by 219.9%，63.0% and 361.4%，respectively，compared with the control.The content of MDA decreased by 54.4%.(3)The addition of humic acid increased the contents of catalase，invertase，urease and phosphatase in the substrate soil，which increased by 37.0%，94.8%，46.5% and 17.0%，respectively，in the 1.5 g/kg humic acid treatment compared with the control.(4)With the increase of humic acid，the effect of promoting the growth of apple seedlings increased first and then decreased.The mass ratio of 1.5 g/kg humic acid had the most obvious effect on apple seedlings.The addition of humic acid significantly increased the fresh weight，dry weight and plant height of apple seedlings，promoted the growth of roots，and effectively increased the leaf enzyme activity and chlorophyll content of the seedlings，and the substrate enzyme activities also had certain increases.Under the experimental conditions，the humic acid with a mass fraction of 1.5 g/kg had the best effect on the growth of apple seedlings.