Abstract: The effect of exogenous hydrogen peroxide on the auxin signal is studied. The GUS was regarded as the reporter gene to research how the auxin signaling proteins, including DR5,a maker of auxin level;AUX1,the auxin input protein; PIN1 and PIN2, auxin output proteins, response to the effects of hydrogen peroxide. The results showed that Arabidopsis thalianas displayed smaller size, shorter root and increased adventitious root number after hydrogen peroxide treatment. The GUS staining results showed that the expression of auxin-related proteins decreased, and suggested that hydrogen peroxide can inhibit the auxin synthesis and transport. Based on the effect of hydrogen peroxide, some antioxidant substances were added to the medium, and the result showed that the phenotype of Arabidopsis and the GUS staining were rescued obviously. Moreover, 0.0001 ?mol/L IAA also could rescue the phenotype of Arabidopsis and the expression of auxin proteins. All the results suggest that the hydrogen peroxide can regulate the plant growth and development by inhibiting the auxin signal.