Objective To investigate the value of soluble triggering receptor expressed on myeloid cells-1(sTREM-1) in the diagnosis of bacterial pleural effusion. Methods The levels of sTREM-1 in pleural effusion were determined in 30 patients with bacterial pleural effusion, 33 patients with malignant pleural effusion,31 patients with tuberculous pleural effusion and 28 patients with transudate by quantitative ELISA assay. The levels of CRP in pleural effusion were assayed using immunonephelometry method. The diagnostic value was assessed by receiver operating characteristic ROC curve analysis. Results The levels of sTREM-1［(1255.2±248.6)ng/L］ in bacterial pleural effusion were significantly higher than those in malignant ［（125.6±22.4）ng/L］, tuberculous［（184.5±36.5）ng/L］ and transudate groups［（92.5±20.8）ng/L］ (P＜0.05). For ROC curve, when the cut off value of sTREM-1 was set at 425 ng/L, the sensitivity , specificity ,accuracy, positive predictive value and negative value was 93.3%,90.3%,91.9%,93.2% and 93.3%, respectively. Conclusions Detection of sTREM-1 in pleural effusion is helpful to differentiate pleural effusion of bacterial origin from those with other etiologies.