Abstract: [Objective] HX2 can biosynthesize indole-3-acetic acid (IAA) and pyrroloquinoline quinone (PQQ).This study aims to focus on mechanisms of pyrroloquinoline quinone and indole-3-acetic acid in plant growth ptomotion of Rahnella aquatilis HX2.[Method]In this study, plant growth, nutrition absorption and root morphology of maize were analyzed by using tube and greenhouse experiments with the treatments of PQQ, IAA, HX2 and its derivative strains.[Result]Compared to the control, PQQ, IAA, and HX2 could significantly promote maize growth, including plant biomass (shoot length, root length, fresh weight and dry weight), plant nutrient (total nitrogen, total phosphorus and total potassium), and in the three treatments, HX2 treatment showed more effects on the maize growth.MH15, which was disrupted by the pqq gene could not produce PQQ, the maize growth also could be promoted compared to control.However, the effect of MH15 was lower than that of HX2 and CMH15(pqq).In PQQ and IAA treatments, slender root length, middle root length, total root length and root surface area of maize were improved, and the root average diameter of maize was reduced compared to the control.In treatment of HX2, root surface area, total root length, thick root length, middle root length and slender root length of maize were improved and maize root system was elongated and coarsened compared to the control.[Conclusion]IAA and PQQ, as promoting factors in HX2, were involved in regulating action in enhancing plant biomass.Also it can improve nutrient intake and enhance root morphology of maize.