The purified elementary bodies of C. pneumoniae TW-183 were used for immunization of male BALB/c mice, the spleen cells of these mice were fused with SP2/0 cells and the hybrid cells were cloned by limiting dilution. One clone that secreted the C. pneumoniae monoclonal antibody (Cpn-McAb) stably was obtained finally. The Cpn-McAb belonged to IgG2b class and anti-Cpn-MOMP; the outcome of micro-immunofluorescence showed its weak cross reaction with the C. psittaci elementary body but it has no cross reaction with C. trachoma elementary body. It has the same speciality of the imported Cpn-McAb. For the evaluation of Cpn-McAb, the peripheral blood mononuclear cell specimens of 454 patients were detected by self-made Cpn-McAb and imported Cpn-McAb at the same time. The positive rates of Cpn-antigen were 53.3% for self-made Cpn-McAb and 52.6% for imported Cpn-McAb,showing high concordance between them (Kappa=0.714). The results showed that self-made Cpn-McAb has almost the same high specificity and sensitivity as imported Cpn-McAb, so the self-made Cpn-McAb may replace imported Cpn-McAb to detect Cpn specific antigen and be helpful to diagnosing and treating the clinical diseases associated with Cpn infection.