Objectives To assess the clinical effectiveness of non-penetrating trabecular surgery versus trabeculectomy for open angle glaucoma. Methods We searched the Cochrane Central Register of Controlled Trials (issue 2, 2007), MEDLINE (1966 to May 2008), EMbase (1980 to May 2008), and CMB-disk (1979 to May 2008). We also hand searched relevant journals and conference proceedings. Data were extracted by two reviewers independently using an extraction form. The Cochrane Collaboration’s RevMan 5.0 software was used for statistical analysis. Results Three RCTs involving 127 participants (144 eyes) with previously untreated open angle glaucoma were included. Meta-analysis showed that compared with non-penetrating trabecular surgery, trabeculectomy increased the proportion of patients with reduced postoperative intraocular pressure (WMD2.78, 95%CI 1.41 to 4.15), improved the operation success rate (RR 0.53, 95%CI 0.37 to 0.77), and reduced the use of postoperative antiglaucoma medication (WMD 0.96, 95%CI 0.84 to 1.08). Non-penetrating trabecular surgery reduced the incidence of postoperative complications (RR 17.00, 95%CI 8.36 to 26.00). Conclusion Since the sample sizes of the included trials are relatively small, and the two procedures are also related to progressive visual field loss and optic disk damage, more well-designed large-scale RCTs are required.