Abstract: Lung cancer is one of the most common cancers in our country. We constantlystudy to improve the diagnostic methods of lung cancer in order to establish a simple, reliable andhigh detection method. In this paper 70 cases of serum in patient with lung cancer and 100 cases of serum in normal individual were detected by electrophoresis and enzyme staining using monocl-onal antibodies by “cock-tail”. The results showed that the positive rate of tumor associated antigen（TAA） in the lung cancer cases was 83% while positive rate of TAA in the normal individual was l0%. The diagnostic mistake rate（false negative rate plus false positive rate） was less than 3o%. Therefore it is an useful method to serological diagnosis in lung cancer.