Abstract: Two human colorectal cancer cell lines with different degrees of radiosensitivity, LOVO and SW480, were received a succession of 0, 2, 4, and 6 Gy X-ray radiation. Then, in 24 h after radiation, the protein spectra of each cell line were measured by SELDI-TOF protein chip so that we could get the differentiated protein expressions of each cell line after different radiation doses. And the differentially-expressed protein peaks showing gradient change in a dose-dependent manner of the two cell lines were detected. Finally, GADD45B, Thioredoxin and Metallothionein 1 (MT1) were screened out through Swiss-Prot database as proteins highly related with radiosensitivity in colorectal cancer. The result shows that radiosensitivity in colorectal cancer can be predicted at protein level and SELDI-TOF protein chip can be used to predict radiosensitivity in colorectal cancer at protein level, thus providing ample choices for individualized radiotherapy.