Objective To explore the clinical diagnostic value of CYFRA21-1 in benign lung disease deriving from epithelium cells.Methods CYFRA21-1 level in serum and hydrothorax was determined by electrochemiluminescence immunoassay. The complex sandwich (KS 19.1 monoclonal antibody-CYFRA21-1[Ru(bpy)3]2+ labeled monoclonal antibody BMI 9.21) was fixed to the bead enclosed avidin by means of biotin-avidin combination, then the luminescence under the influence of perfluorotripropylamine and electric field luminous was tested for CYFRA21-1.Results The level of CYFRA21-1 in the group suffering from lung disease accompanied by complications was significantly higher than that of single lung disease group (P<0.01). CYFRA21-1 value in the elder group was significantly higher than that of the younger group (P<0.01).Conclusion The gerontal patients suffering from benign lung disease accompanied by complications should be given symptomatic treatment if their CYFRA21-1 level is elevated but CEA and NES was normal. Recheck the above indices two weeks later so as to identify the benign or malignancy of the disease.