Abstract: In order to study the intraoperative radiation dose fo colorectal carcinoma, cell line LS174T was radiated once in vitro by electron beams at the dose of 0,5,10,20,25 and 30 Gy, then the cell survival ratio and colony forming rate were measured. It is demonstrated that the majority of tumor cells were killed at the dose of 10-30 Gy. The data indicated that the optimal intraoperative radiation dose should be over 10Gy, and that intraoperative radiation should be combined with preoperative or post operative radiation and chemotherapy to reduce postoperative recurrence rate of colorectal carcinoma.