Leukemia is a type of malignant tumor affecting hematopoietic system. Cervical cancer is a malignant tumor of female reproductive tract. The relationship between Calmodulin 3 (CALM3) and leukemia, cervical cancer remains unclear. Leukemia dataset GSE26294 and cervical cancer dataset GSE173097 profiles were downloaded from gene expression omnibus. Principal component analysis, differentially expressed genes (DEGs) screening, weighted gene co-expression network analysis (WGCNA), functional enrichment analysis, gene set enrichment analysis, immune infiltration analysis, protein–protein interaction network construction and analysis, survival analysis were performed. Gene expression heatmaps were plotted. Comparative Toxicogenomics Database (CTD) was used to find diseases most related to core genes. 77 DEGs were identified. According to gene ontology, in biological process category, they were mainly enriched in cell proliferation, immune response, and apoptotic process. In cellular component category, they were mainly enriched in nucleus and Golgi apparatus. In molecular function category, they were mainly enriched in DNA binding, protein binding, transcription factor activity. In Kyoto encyclopedia of gene and genome analysis, they were mainly enriched in cell adhesion molecules, Wnt signaling pathway, cAMP signaling pathway, cGMP-PKG signaling pathway, and basal cell carcinoma. The soft-threshold power in WGCNA was set to 1, generating 6 modules. Finally identifying 3 core genes (CALM3, secreted frizzled-related protein 4, plasminogen). CTD analysis revealed that core genes were related to leukemia, coagulation disorders, vaginal tumors, cervical tumors, autoimmune diseases, and inflammation. CALM3 is lowly expressed in leukemia samples and highly expressed in cervical cancer samples.