Objective To observe the change of leucocyte classification in leucocyte decreasing rats induced by cyclophosphamide.Methods\ Cyclophosphamide (30/kg) was injected into rats' abdominal cavity for five days,while in the control group,isovolumic normal saline was injected.Results\ The total of leucocyte in peripheral blood decreased markedly( p <0 01),which maintained for 15 days after stopping dosing.In the mean time,band\|form granulocyte increased (p<0.01),even if stopping dosing 15 days;segmented granulocyte reduced (p<0.01),but it returned after stopping dosing.Cyclophosphamide had no effect on lymphocyte.Conclusion\ Cyclophosphamide caused the change of leucocyte count and its classification, with band\|form granulocyte increased and segmented granulocyte reduced,which could be used as experimental indications.