Abstract: ‘Honey-melon’ was used as experimental material, seedlings were adopted to the hole disc.Peat∶vermiculite∶perlite was mixed according to 1∶1∶1（volume ratio） as the nursery substrate.The effects of different concentrations of nitrogenous fertilizer(0,10,20,30,40 mg·plant^-1) on the physicochemical properties, microbial population, growth and nutrient accumulation of melon seedlings were studied, in order to provide reference for improving the efficiency of nitrogen fertilizer, cultivating high-quality strong seedlings.The results showed that the physical and chemical properties of seeding substrate could be improved by applying a certain concentration of nitrogen fertilizer.Under T2 treatment, in other words, when nitrogen concentration was 20 mg per plant, the number of bacteria, fungi and actinomycetes in the matrix decreased significantly.In contrast to CK,the plant height increased significantly by 47.22%,stem diameter increased by 36.78%,root length increased by 46.86% and leaf area of melon seedlings increased by 33.06%.The fresh weight of overground was 36.04% higher than that of CK.The melon seedlings with the highest chlorophyll content was T2 treatment, which significantly increased by 35.52% in comparison with the CK.Adding a certain concentration of nitrogen fertilizer could significantly promote the accumulation of nitrogen content in plants, while the contents of P and K remained unchanged.In conclusion, when the nitrogen concentration was 20 mg per plant, the physical and chemical properties of the matrix were effectively improved, and the growth of melon seedlings were the best, which could be used as the best nitrogen supplemental level for melon seedings.