Objective To systematically evaluate the effectiveness and safety of mepolizumab in treating eosinophilic asthma. Methods Databases including PubMed, Embase, ISI Web of Science, Cochrane CENTRAL, MEDLINE, VIP and CNKI were searched to collect randomized controlled trials (RCTs) about mepolizumab for eosinophilic asthma from inception to October 2016. The references of these articles and relevant conference information were also manually retrieved. Meta-analysis was performed by RevMan 5.1 software after two researchers independently selected the literatures, extracted data and evaluated the quality according to the inclusion and exclusion criteria. Results A total of 9 RCTs involving 2273 patients were included. Compared with the control group, the acute exacerbation rate of asthma was decreased significantly in the mepolizumab treatment group [RR=0.67, 95%CI (0.53, 0.85), P=0.0009], eosinophil count in blood was significantly reduced [MD=–0.22, 95%CI (–0.29, –0.15), P<0.00001], eosinophil count in sputum was also significantly reduced [MD=–6.37, 95%CI (–9.68, –3.06), P<0.0002], and the proportion of patients with increased asthma-related quality of life (ACQ) score was higher significantly. The overall incidence of adverse reactions was similar between two groups [RR=0.90, 95%CI (0.71, 1.14), P=0.39]. The incidence of serious adverse reactions of mepolizumab treatment was superior to that of placebo [RR=0.45, 95%CI (0.23, 0.89), P=0.02]. The overall incidence of cardiovascular events was comparable between placebo and mepolizumab treatment [RR=0.95, 95%CI(0.40, 2.22), P=0.90]. Mepolizumab treatment may have a role in improving lung function, but the effect was not obvious. Conclusion Mepolizumab treatment can reduce the number of eosinophils in blood and sputum, reduce the exacerbation rate, and improve the quality of life of asthmatic patients with better safety.