Abstract: Objective To investigate the expression of miRNA related to malignant pleural effusion in lung adenocarcinoma， and to investigate the relationship between the expression of miRNA and prognosis. Methods miRNA chip technique was used to screen the expression of malignant pleural effusion in 10 lung adenocarcinoma patients， and to analyze the possible correlation of miRNA with clinical prognosis. The expression of miRNA was detected by quantitative real-time PCR（QPCR）in 84 cases of malignant pleural effusion of lung adenocarcinoma， and the differential expression of miRNA was confirmed by clinical prognosis analysis. Results In 5 patients of progression free survival （PFS） more than 5 months and 5 patients of PFS less than 2 months， microarray screening revealed a total of 13 miRNAs expression changing ratio＞2 times. Expression of miR-146a， miR-16， miR-155， miR-484， miR-134， miR-141， miR-106b and miR-93 was detected in 84 patients with pleural effusion of different prognosis. It was revealed that the expression of miR-93 and miR-146a were different. Compared with patients with poor prognosis， the expression of miR-93 was increased by 2.41 times in patients with good prognosis； and the expression of miR-146a was decreased by 46％. Conclusion MiR-93 is highly expressed and miR-146a is lowly expressed in malignant pleural effusion of patients with better prognosis. They may be new molecular markers for the prognosis of patients with malignant pleural effusion.