Abstract:【Objective】In order to improve the technical level of industrialized seedling culture and find new methods to make use of plant growth-promoting rhizobacteria (PGPR), a new strain of functional bacteria that would promote growth of watermelon was isolated, cultured and inoculated into ordinary nursery substrate, thus forming a kind of bio-nursery substrate. 【Method】 A number of strains of bacteria were isolated randomly from the rhizosphere soil of watermelon plants and screened by plant growth-promoting properties. One strain which was found to possess complex functions and efficient rhizospheric colonization ability was further cultured and then inoculated into in ordinary nursery substrate in developing bio-nursery substrates. Repeated seedling nursing tests and pot experiments were performed in greenhouse and subsequently in the field to further validate effect of the novel bio-nursery substrate prepared by inoculating this bacterial strain into ordinary nursery substrate. In the end this strain was proved to be the right one for preparation of bio-nursery substance. 【Result】 Through screening, a strain of bacteria, N23, capable of both producing indole acetic acid and NH3 simultaneously and acting in antagonism against Fusarium oxysporum f. sp. niveum and Ralstonia solanacearum, was isolated from the rhizospheric soil of watermelon plants. Seedling raising experiments show that in the substrate inoculated with Strain N23, watermelon seedlings grew much better than those in the ordinary nursery substrate, in plant height, stem diameter and leaf area. Such an effect was further demonstrated in another three seedlings raising experiments, showing that the strain steadily promotes seedling growth in a number of growth indices. The pot experiments show that the plants growing in the bio-nursery substrate were significantly higher than those in the ordinary nursery substrate, in all measured parameters except SPAD (Soil and Plant Analyzer Development), which differed very slightly. In the field experiments, watermelon, cucumber, tomato, and pepper seedlings cultured in the bio-nursery substrate grew better than those cultured in ordinary nursery substrate, in plant height and stem diameter, which coincided with the results in the pot and seedling experiments. And in the two seasons of field experiments, the watermelon in the former was 12.5% and 25.4% higher than that in the latter, respectively. In the field experiments cucumber, tomato, and pepper in the former was 18%, 60% and 25%, than their respective one in the latter. Morphological and biochemical analysis and 16S rDNA gene sequencing of Stain N23 shows that the strain is one of Bacillus sp. 【Conclusion】 All the findings in this study demonstrate that the bio-nursery substrate prepared by inoculating Bacillus sp. N23 into ordinary nursery substances promotes seedlings and plant growth as well as yield of the crop. Consequently, this study has provided some novel ideas for making use of rhizobacteria and some theoretical and technical support to the development of PGPR agents for preparation of bio-nursery substances.