Objective: To explore the validity and effectiveness of multifocal electroretinogram (mfERG) technology in the diagnosis of primary open-angle glaucoma (POAG). Methods: In this case-series study, 60 POAG patients (86 eyes) who were diagnosed in the First People's Hospital from October 2014 to March 2016 were enrolled in the glaucoma group. There were 20 cases (27 eyes) of early POAG, 20 cases (29 eyes) of middle POAG, and 20 cases (30 eyes) of late POAG. Another 60 healthy subjects (120 eyes) were enrolled in the normal control group. All subjects in both groups received an mfERG examination for diagnostic testing. The density values and latency period of the P1 wave in every second-order reaction ring and quadrant were observed and compared. All data were analyzed using one-way analysis of variance and the χ2-test. Results: There was no change in the P1 wave density values in rings 1-5 between early glaucoma group and control group. However, the density values of the P1 wave in the inferior temporal and superior temporal quadrants in the early glaucoma group declined compared with those in control group (P<0.05). In the middle stage glaucoma group, the P1 wave response density value in rings 2-5 and the four quadrants declined compared with those in the control group (P<0.05). In the late glaucoma group, the density values of the P1 wave in rings 1-5 were also lower than those in the normal group (P<0.05). The latency periods of the P1 wave in rings 1-5 and in the four quadrants of every stage of glaucoma were prolonged compared with those in the control group (P<0.05). However, latency periods in the late glaucoma group were even more extended (P<0.05). Conclusions: The latency period and density changes of the P1 wave in rings 1-5 in mfERGs reflect retinal damage in glaucoma. These changes have clinical value in the diagnosis of early glaucoma.