In recent years, the interactions between bacterial-feeding nematodes and bacteria and their ecological functions in terrestrial ecosystems have been recognized to play a crucial role in soil ecology. Many studies have found that bacterial-feeding nematodes increased soil mineralization and improved the supply of inorganic nitrogen, subsequentlystimulating plant growth. The nutrient effect of the soil bacterial-feeding nematodes on root development has been investigated in a microcosm, while the auxin effect remains controversal. An indole acetic acid (IAA)-producing bacteria and two species of bacterial-feeding nematodes were isolated, screened and identified from our experimental soil. Then, a study on the effect of the interaction between aboriginal bacterial-feeding nematodes and IAA-producing bacteria on soil IAA content was implemented in a gnotobiotic microcosm experiment. In the gnotobiotic microcosm experiment, two species of aboriginal nematodes (Cephalobus sp. and Mesorhabditis sp.) grazing on bacteria stimulated both the bacterial growth and activity and increased the mineral nitrogen. The interactions between IAA-producing bacteria and bacterial-feeding nematodes significantly increased soil IAA content. This increase was influenced by bacterial-feeding nematode species and incubation time. Mesorhabditis sp. (cp 1) significantly stimulated the growth of the IAA-producing bacteria at day 10 and day 20. However, compared with Cephalobus sp. (cp 2), Mesorhabditis sp. more significantly increased soil IAA content at day 10 and day 30.