Abstract: In this paper, the effects of irradiation on the polyetherketone with cardo group(PEK-C) are studied. It is found that PEK-C can be crosslinked by irradiation under vacuum, while degradation reaction occurs in PEK-C at room temperature in the presence of air. It is also found that the crosslinking degree of PEK-C is far larger at high temperature(300℃) than at room temperature. In the case of the same gel content, Tg value of the crosslinked PEK-C at high temperature is higher than that at room temperature and is about 20℃ higher than that of unirradiated PEK-C. Gelation dose of PEK-C at 300℃ under vacuum is 1.5×104Gy.