In this paper, using the method of turbidimetric technique, changes of rabbit platelet aggregation are observed following ,γ, ray whole-body irradiation with 400 rads. The results indicated that the function of blood platelet aggregation was risen from the first to the fifth day after radiation, but reduced at the seventh day and markedly at the tenth. It is believed that the early elevation of platelet aggregation may result in increase of adherence omd coagulation, and enhance microcirculation disturbances. In addition, a large number of platelets and coagulation factors were consumed, it might be one of the causes of hemorrhage syndrome after exposure. During early therapy of radiation injury, therefore, it is of benefit for improving the repair of radiation injury to inhibit platelet aggregation.