In this study, germinated 24h wheat seeds were inoculated with Azorhizobium caulinodans, samples were collected at 0, 6, 12, 24, 48, 72 and 96 h, respectively and 6 miRNAs (miR156, miR159, miR160, miR167, miR168 and miR403)in wheat leaves, 3 of these miRNAs’ target genes were detected using Realtime quantifying PCR. The distribution of GFPlabeled A. caulinodans in 8 d wheat leaves were detected via confocal microscopy, and relevant physiological indices were measured and compared. The results showed that: (1) GFPlabeled A. caulinodans could colonize in margin area of wheat leaves. (2) All 6 miRNAs relating to growthpromoting varied in different degrees after treatment with A. caulinodans, and soared to their peaks at 12-24 h. The peak of miR159 was 2.88 times as strong as regular expression. (3) The expression of 3 miRNAs’ target genes were corespondent to their upstream miRNA, but not restrict. (4) Physiological indices of length and fresh weight of leaves showed sensible growth promoting, the weight of leaves in 96 h showed significant difference statistically (P<0.01). The study suggested that: A. caulinodans inoculated in wheat could colonize leaves, exerting evident growthpromoting effect to wheat leaves, and miRNAs play an intrinsic role in the growthpromotion.