Objective：To investigate the expression of Rho GTPase activating protein 44（ARHGAP44） in colorectal tissue and its relationship with the clinicopathological characteristics and prognosis of colorectal cancer in multiple data sets. Methods：With the use of the gene expression omnibus（GEO） and the cancer genome atlas（TCGA） cohorts，we summarized the expression of ARHGAP44 and its relationship with clinicopathological characteristics of colorectal cancer，evaluated the prognostic value by the Cox regression model and Kaplan-Meier curve. The mRNA expression of ARHGAP44 was validated in clinical samples by RT-qPCR. And gene set enrichment analysis（GSEA） was used to predict the pathway. Using the ssGSEA（single-sample gene-set enrichment analysis） algo－rithm，the association between ARHGAP44 and immune cell infiltration was calculated. Results：In TCGA，GEO datasets and clinical samples，the ARHGAP44 expressions were reduced in tumor tissues（P<0.001），and related to T stage and TNM stage（P<0.05）. The low expression of ARHGAP44 showed an independent risk factor for OS（overall survival）of colorectal cancer patients（HR=0.44，P=0.02）. GSEA results showed that the high expression samples of ARHGAP44 were rich in colorectal cancer pathway，Notch pathway，T cell receptor pathway，B cell receptor pathway and other gene sets. The expression of ARHGAP44 was negatively correlated with the infiltration levels of macrophages，T helper cells，TIL（tumor-infiltrating lymphocytes） and typeⅠIFNresponse（cor=-0.35，-0.37，-0.33，-0.35，-0.23 and -0.32，P=0.008，0.006，0.027，0.021，0.041 and 0.021）. Conclusion：The expression of ARHGAP44 is down-regulated in colorectal cancer，which can be used as an independent prognostic biomarker for survival，and has a potential role in tumor immunology.