Objective The aim of this study was to investigate the relationship between miR-7-5p expression and intertissue-125I irradiation sensitivity in pancreatic cancer tissues and to analyze the function of target genes. Methods Thirty-seven patients with unresectable pancreatic ductal adenocarcinoma (PDAC) treated with radioactive 125I seed implantation were enrolled. RT-PCR was used to detect the expression level of miR-7-5p in cancer tissues and analyze the relationship between miR-7-5p expression and 125I radiation sensitivity. Bioinformatic software and online tools were used to predict the miR-7-5p target genes and analyze their functional annotation and pathway enrichment. Results Radioactive 125I seed implantation was followed up for 2 months. The objective response rate of the miR-7-5p high expression group was 65.0％ (13/20), whereas the objective response rate of the miR-7-5p low expression group was 5.88％ (1/17), and the difference between the two groups was statistically significant (χ2 = 13.654, P < 0.001). A total of 187 target genes were predicted using three databases. GO functional annotation showed that target genes were mainly involved in cellular response to insulin stimulus, regulation of gene expression by genetic imprinting, cytosol, peptidyl-serine phosphorylation, bHLH transcription factor binding, cargo loading into vesicles, cellular response to epinephrine stimulus, and nucleoplasm. KEGG pathway enrichment analysis showed that target genes were mainly involved in the ErbB signaling pathway, HIF-1 signaling pathway, axon guidance, longevity regulatory pathway, endocrine resistance, glioma, choline metabolism in cancer, and EGFR tyrosine kinase inhibitor drug resistance. Molecular complex detection analysis by Cytoscape revealed that PIGH, RAF1, EGFR, NXT2, PIK3CD, PIK3R3, ERBB4, TRMT13, and C5orf22 were the key modules of miR-7-5p target gene clustering. Conclusion The expression of miR-7-5p in pancreatic cancer tissues positively correlated with the radiosensitivity of 125I seeds. Via targeted gene regulation, miR-7-5p acts on the network of multiple signaling pathways in PDAC and participates in its occurrence and development. Thus, miR-7-5p may become a predictive index of 125I seed implantation therapy sensitivity in PDAC patients.