To determine the therapeutic effect of nootropic agent Cerebrolysin on patients with mild to moderate Alzheimer's disease (AD), we searched the Cochrane Library, Medline, PubMed, and Chinese Biomedical Literature Analysis and Retrieval System for Compact Disc (CBMDISC), and communicated with EBEWE Pharmaceutical Ltd, for randomized trials comparing Cerebrolysin with placebo in AD. Available data on clinical global impression, cognitive performance and activities of daily living were extracted from 6 randomized double-blind placebo-controlled clinical trials and combined with standard meta-analysis methods. An infusion with Cerebrolysin for 4 weeks (30 ml Cerebrolysin daily on five consecutive days of each week) led to a significant improvement of the clinical global impression. Compared with placebo, log(OR) was 1.1799, and 95% confident interval was 0.7463-1.6135 (P < 0.05), indicating that Cerebrolysin could significantly improve the clinical global impression in patients with mild to moderate AD. However, more convincing evidences are needed for the efficacy of Cerebrolysin on the cognitive performance and activities of daily living.