Abstract: In order to provide theoretical basis for scientific and rational application of organic fertilizer in seedling breeding, the effects of different proportions of organic fertilizer on growth and soil fertility of Pinus sylvestris var. mongolica were studied. Under field conditions, the experiment was set up with 4 treatment, namely blank control (T1), chemical fertilizer control (T2), 50% organic fertilizer (T3) and 100% organic fertilizer (T4), and repeated three times. The results showed that: the dry matter accumulation in root, stem and leaf of T3 increased by 65.92%, 46.51% and 36.54% respectively compared with that of T2, and there was no significant difference in total dry matter accumulation between T4 and T1, T2. Root-shoot ratio of T4 was significantly higher than that of T1 and T2. Compared with T2, the soil bulk density at T3 decreased by 17.02%, and the total porosity, capillary porosity, non-capillary porosity and saturated water content of T3 and T4 were significantly higher than those of T1 and T2. The available nitrogen, available phosphorus and available potassium of T3 was higher than T2 by 18.17%, 21.28% and 6.17% respectively, and the content of organic matter and total nitrogen in T3 and T4 were significantly higher than those in the control; Compared with T2, T3 significantly increased the activities of urease, polyphenol oxidase, protease and sucrase, and significantly decreased the activities of catalase. Comprehensive analysis indicated that 50% organic fertilizer was the best for promoting seedling growth and improving soil fertility.