In this study, peach fruit "Xiaobaifeng" was treated with different concentrations of exogenous IAA (200 μmol L-1, 10 μmol L-1 and 0.1 μmol L-1) at the second rapid expansion stage. Samples were collected at 10, 20 and 30 days after treatment. The changes of hardness, sugar components (sucrose, glucose, fructose, sorbitol), pectin, cellulose content and ethylene release of peach fruit were analyzed. The transcriptomic sequencing was performed on fruits treated with 200 μmol L-1 IAA for 30 days and in the control group. The results showed that（1）At 30 days after IAA treatment, the pulp hardness of 200 μmol L-1 treatment group was significantly increased compared with the control group, and the average maturity was delayed by 5 days, while there were no significant difference of 10 and 0.1 μmol L-1 IAA treatment group with the control group at the same time. （2） Sucrose content was significantly lower than that of the control group after 0.1 and 200 μmol L-1 IAA treatment for 30 days, but had no significant difference with that of the control group after 10 μmol L-1 IAA treatment for 30 days. There was no significant difference in the contents of glucose, fructose and sorbitol at 30 days after IAA treatment. （3）The content of soluble pectin after 0.1 μmol L-1 IAA treatment was not significantly different from that of the control group at 30 days, but was significantly lower than that of the control group at 10 and 200 μmol L-1 IAA treatment at 30 days; At 30 days after IAA treatment, there was no significant difference between the contents of insoluble pectin and cellulose in peach pulp and the control group.（4）At 10, 20 and 30 days after IAA treatment, there were no significant difference in ethylene release of 0.1 and 10μmol L-1 treatment with the control group, and the 200 μmol L-1 treatment group was significantly lower than the control group. （5）Transcriptome data showed that there were a total of 86 differentially expressed genes between the 200 μmol L-1 IAA treatment and the control group. KEGG analysis found that the expression profiles of multiple genes in 6 metabolic pathways closely related to fruit development and maturation had significant changes, and the change trend was consistent with the measured physiological indicators data. Comprehensive analysis showed that 200 μmol L-1 exogenous IAA treatment of peach fruit at the second rapid expansion stage could delay the fruit ripening process.