Influence of rare earth on longitudinal impact property of carbon - manganese steel has been studied using digital impact test machine. The results show that at room temperature the effect of cerium on impact energy is not evident and lan-thanum reduces it. At - 60℃, rare earth can improve impact energy while its content is 0. 005% but deteriorate it while it content is excessive. Appropriate content of rare earth is beneficial to increase energy which is absorbed in the course of crack spread. The action o...