Aim Thymosin-alphal (TA), used as an immune modulator in clinics, has limited studies about its effect on cancer cells.Here we aim to investigate the role of TA in the immunotherapy of iNKT cells against colon cancer.Methods Paired blood samples and fresh tumor specimens were collected from 9 colorectal cancer(CRC) patients; pure iNKTs were obtained by FACS of the concentrated leucocytes of healthy subjects.The cell proliferation was determined by CSFE labeling, cytotoxicity of iNKT cells against target cells was performed with LIVE/DEAD Viability/Cytotoxieity Kit, and blocking assays were applied to determine the mechanisrns of iNKT cell-mediated toxicity.qRT-PCR and western-blot were also performed to determine the mechanism of TA worked on cancer cells.