Abstract: A composition contains Phragmitis Rhizoma extract as an active ingredient. As a result of treating mouse bone marrow cells with an extract of Phragmitis Rhizoma, it was confirmed to have an effect that a decrease in colony of hematopoietic cells, which is induced by an anticancer agent, is significantly recovered and bone marrow suppression caused by an anticancer agent is significantly recovered in an animal model which has been induced to have bone marrow suppression according to intraperitoneal injection of an anticancer agent. Thus, the Phragmitis Rhizoma extract can be advantageously used for a composition for prevention, amelioration, or treatment of a disorder caused by side effect of an anticancer agent, and there is a possibility of having the increased effect of an anticancer agent when it is used as an anticancer adjuvant in combination with an anticancer agent.