ObjectiveTo investigate the diagnostic value and potential mechanism of miR-15b-5p in head and neck squamous cell carcinoma (HNSCC) by using bioinformatics.Methods(1) Expression data of miR-15b-5p in HNSCC and/or clinical data of HNSCC patients were collected from the GEO and TCGA databases. Expression of miR-15b-5p in HNSCC and its value for diagnosing HNSCC were analyzed by Meta-analysis. The SPSS 26.0 software was used to analyze the relation between miR-15b-5p expression and clinical characteristics of HNSCC patients. The real-time fluorescent quantitative PCR was employed to detect miR-15b-5p expression in HNSCC cells and normal cells. (2) The downstream target genes of miR-15b-5p and differentially expressed genes of HNSCC were screened from the databases of miRWalk and GEPIA2, respectively, after performing intersection of the two, the key target genes of miR-15b-5p in HNSCC were obtained. The enrichment analysis was performed on the key target genes. (3) Expressions and methylation levels of partial target genes in HNSCC were analyzed by using the UALCAN database. The relation of expressions of partial key target genes with disease-free survival and overall survival of HNSCC patients was analyzed by employing the GEPIA2 database. Results(1) The results of Meta-analysis revealed that miR-15b-5p exhibited a high expression in HNSCC (P<0.05). Compared with normal cells, expression of miR-15b-5p was elevated in HNSCC cells (P<0.05). The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio of miR-15b-5p expression in the diagnosis of HNSCC were 0.70, 0.72, 2.15, 0.48, and 7.33, respectively, and area under the summary receiver operating characteristic curve was 0.81. Male patients, and patients with age<60 years old, in N1-N3 stage obtained a higher miR-15b-5p expression as compared with female patients, and patients with age≥60 years old, in N0 stage, respectively (P<0.05). (2) A total of 54 key target genes of miR-15b-5p in HNSCC were obtained. The results of functional enrichment analysis revealed that the key target genes were closely related to extracellular matrix, and the results of pathway enrichment analysis indicated that the key target genes were closely related to multiple signaling pathways, containing retinol metabolic pathway. (3) Compared with normal tissues, expressions of the key target genes RDH12 and UGT1A7 were down-regulated in HNSCC tissues, and methylation levels of the key target genes UGT1A10 and UGT1A7 were decreased in HNSCC tissues (P<0.05). HNSCC patients with high UGT1A7 expression obtained a longer disease-free survival than those with low UGT1A7 expression (P<0.05), but there was no statistically significant difference in overall survival between the two (P>0.05). ConclusionThere is a close correlation between miR-15b-5p and the occurrence and development of HNSCC, and miR-15b-5p has a potential diagnostic value on HNSCC. MiR-15b-5p may participate in the regulation of retinol metabolism signaling pathway by targeting UGT1A7 and RDH12 genes, thereby affecting the occurrence and development of HNSCC.