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ABSTRACT Although WRKY transcription factors play crucial roles in plant responses to high‐temperature stress, little is known about Group IIb WRKY family members. Here, we identified the WRKY‐IIb protein PlWRKY47 from herbaceous peony (Paeonia lactiflora Pall.), which functioned as a nuclear‐localized transcriptional activator. The expression level of PlWRKY47 was positively correlated with high‐temperature tolerance. Silencing of PlWRKY47 in P. lactiflora resulted in the decreased tolerance to high‐temperature stress by accumulating reactive oxygen species (ROS). Overexpression of PlWRKY47 improved plant high‐temperature tolerance through decreasing ROS accumulation. Moreover, PlWRKY47 directly bound to the promoter of cytosolic glyceraldehyde‐3‐phosphate dehydrogenase 2 (PlGAPC2) gene and activated its transcription. PlGAPC2 was also positively regulated high‐temperature tolerance in P. lactiflora by increasing NAD+ content to inhibit ROS generation. Additionally, PlWRKY47 physically interacted with itself to form a homodimer, and PlWRKY47 could also interact with one Group IIb WRKY family member PlWRKY72 to form a heterodimer, they all promoted PlWRKY47 to bind to and activate PlGAPC2. These data support that the PlWRKY47‐PlWRKY47 homodimer and PlWRKY72‐PlWRKY47 heterodimer can directly activate PlGAPC2 expression to improve high‐temperature tolerance by inhibiting ROS generation in P. lactiflora. These results will provide important insights into the plant high‐temperature stress response by WRKY‐IIb transcription factors. [ABSTRACT FROM AUTHOR]