[Objectives]  To investigate the function of the heat shock protein Hsp90 gene of Bactrocera cucurbitae (Coquillett) (Bc-Hsp90) under different temperatures and pesticide stress in order to improve control of this pest. [Methods] The cDNA full-length fragment of the Bc-Hsp90 was cloned using the RACE-PCR method. Bioinformatics tools were used to analyze the sequence characteristics, and real-time quantitative PCR was used to detect the expression levels of the gene under heat stress, and after exposure to the pesticide abamectin, in abamectin-resistant and susceptible strains. [Results]  The complete sequence of 2 654 bp was obtained (Accession number: KP864677) and was found to contain a 2 145 bp open reading frame (ORF) encoding 715 amino acids. Family signatures of the HSP90 protein and the cytoplasm of the Hsp90 gene C-terminal region MEEVD motif were detected. Phylogenetic analysis indicates that Bc-Hsp90 is highly conserved. Real-time quantitative PCR results showed that 1 h and 2 h of heat stress（32-40℃）up-regulated the expression of Bc-Hsp90. Expression peaked at 38℃ and 40℃ and expression in an abamectin resistant strain (RS) was 2.13 times higher than in a sensitive strain (SS). The expression of the Bc-Hsp90 gene was down-regulated after exposure to an LC₉₀ dose of abamectin and returned to normal levels after 96 h. [Conclusion] The expression level of Bc-Hsp90 could play an important role in heat resistance and pesticide tolerance in B. cucurbitae.