Objective To investigate the infection status of HIV/AIDS patients complicated with pneumocystis Carinii Poneumonia(PCP),and the role of CD4+ T lymphocyte in PCP.Methods PC was detected by Giemsa's staining and CD4+ T lymphocyte was counted by flow cytometry.Meanwhile,this text calculated and compared a series of indexes about PC infection,such as the total positive rate,the average annual positive rate,the average monthly positive rate,the positive rate between female and male,the positive rate between sputum and BALF specimens,and the relationship between the positive rate and CD4+ T lymphocyte count.Results The total positive rate about PC infection of the 1 806 eases of sputum specimens was 46.8％,and the incidence mainly from April to July during a year,and the positive rates were 46.3％ and 50.2％ for males and females respectively.The results showed that there were no significant differences when compared with the average annual positive rate ( P ＞ 0.05 ),but there were significant differences when compared with the average monthly positive rate ( P ＜ 0.05 ),the positive rate between female and male(P＞0.05),and among 3 formerly defined ranges of CD4+count(P ＜0.05).Conclusion Giemsa's staining showed the total positive rate was 46.8％ of the HIV/AIDS patients infected by PC with sputum specimens,which represented a seasonal fluctuation tendency.The positive rate of BALF was higher than that in sputum,and it increased with CD4+ count decreasing.Giemsa's staining was an efficient,simple and feasible way for PC detection and easy for generalization.Meanwhile,it is strongly relied on the operator's experience and skill.