Objective To investigate the expression of MEX3A in colorectal cancer (CRC), and to explore the effect and mechanism of MEX3A on the proliferation and migration of colorectal cancer cells.   Methods Totally 327 cases of data(41 normal tissues and 286 tumor tissues) were obtained from TCGA database, and 104 cases of clinical samples(77 cases tissues and 27 paracancerous tissues) were collected for immunohistochemistry, then analysed the differences in MEX3A expression between CRC tissues and normal tissues. Western blotting and immunofluorescence staining were used to evaluate the differential expression of MEX3A in CRC cell lines.  CL187 cells were selected as the follow-up research vector. Small interfering RNA of MEX3A(siMEX3A) was transfected into CL187 cells to inhibit the expression of MEX3A. The proliferation and migration of CL187 cells were measured by MTT, colony formation assay and Transwell assay. The expression of PI3K, p-PI3K, Akt and p-Akt were detected by Western blotting.   Results TCGA database, immunohistochemistry and Western blotting analysis showed that MEX3A was highly expressed in colorectal cancer. The result  of immunofluorescence staining showed that MEX3A was concentrated in the cytoplasm and the nucleus. In MTT, colony formation assay and Transwell assay, the proliferation and migration ability of CL187 cells in siMEX3A group decreased significantly than those in control group (P<0.05). Western blotting result  showed that the expression of p-PI3K and p-Akt in siMEX3A group down-regulated significantly (P<0.05), and the inhibition of proliferation and migration ability of CL187 cells induced by siMEX3A group could be reversed by 740 Y-P via activating the PI3K/Akt signaling pathway.   Conclusion MEX3A is highly expressed in colorectal cancer and promotes the proliferation and migration of CRC cells via PI3K/Akt signaling pathway.