Objectiveive To establish a model of white blood cell(WBC) and marrow nucleated cell decreasing in rats. Methods Twenty SD rats were randomly divided into experimental group and control group. In experimental group, cyclophosphamide (30 mg/kg) was injected into rats' abdomen cavity once a day for 5 days,and in control group ,rats were treated with isovolumetric normal saline only. The total of WBC and the number of marrow nucleated cells as well as body weight were monitored. Results In experimental group,the total of WBC in peripheral blood and the number of marrow nucleated cells decreased significantly (P<0.01).The total of WBC was reduced to minimum by the end of the fifth dosing day,and the low level of WBC maintained for 15 days after stopping dosing ,which could provide ample observation time for experimental study. In addition ,rats lost body weight markedly compared with that in control group (p<0.01). Conclusion It was feasible and practical that cyclophosphamide induced the model of WBC and marrow nucleated cell decreasing in rats. Such animal pattern could be used to screen drugs for diminishing chemotherapy toxicity and to develop other therapy methods.